Louis Pasteur

Founder of Microbiology

by

Mary June Burton

Grade Level and Copyright

Grade Level is 10.3 using the Flesch-Kincaid readability test with three sample chapters.

First edition published by Franklin Watts, 1963.

Electronic edition published by Ebooks for Students, Ltd., 2021.

This ebook is in the public domain, and is free of all copyright restrictions. It is also free of digital rights management protection so you can distribute copies to your students, their parents, and other prospective readers.

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Comments  or questions to support@ebooksforstudents.org or (202) 464-9126.

The author wishes to acknowledge with thanks the permission granted by the French publishers to translate and quote from Correspondance de Pasteur, reunie et annotee par Pasteur Vallery-Radot. Volume I is copyrighted by Editions Bernard Grasset, Paris; Volumes 2, 3, and 4, by Editions Flammarion, Paris.

Publisher's Note about Biology Labs

Louis Pasteur was one of the most important scientists of human history. He helped us understand that while some unicellular organisms are beneficial, such as yeast in baking bread and brewing beer, others are harmful like e.coli and other coliform bacteria. His research inspired the British surgeon Joseph Lister to encourage physicians to implement appropriate hygienic practices during medical procedures, which decreased the number of post-operative deaths from gangrene. Post-surgery deaths from gangrene plummeted due to the work of Pasteur and Lister.

The author describes Pasteur's experiments—both successful and unsuccessful—in detail. You will see how his experimental data lab work confirmed his ideas, and where he had to consider alternative hypotheses after seeing what nature did in the lab. If your teachers decide that some hands-on practice with unicellular organisms would be a valuable experiment for you in your labs, we have included some possible experiments below. The simplest experiment is presented first.

As you evaluate Pasteur's contributions to science in the pages that follow, remember that in his age, most doctors believed that infections occurred spontaneously— independent of harmful microbes. Germs, bacteria, microbes were not known as agents of disease.

Presumably, it is safe to allow butter to become rancid in a middle school or high school lab, and then study the results as Pasteur did at the beginning of Chapter 8. What was Pasteur's mistake in the experiment with the rancid butter? What did he first think the bacteria were—animals or plants? Could you duplicate this experiment in your biology lab and see what the results are? Will a lack of air kill the bacteria swarming around your slide?

Here is the excerpt from Chapter 8 which describes Pasteur's experiment with rancid butter.

Chapter 8

While studying the fermentation which produces butyric acid (the acid formed as butter becomes rancid), Pasteur made a surprising discovery.

Under the microscope, he saw some very tiny, short rods, rounded at the ends. They were spinning about and shaking themselves, sometimes bending almost double. So lively were they that he assumed they were microscopic animals or “animalcules” as they were sometimes called.

“They must be feeding on the microorganisms that produce the butyric acid ferment,” the scientist mused. “I’ll have to get rid of them.” Finally he realized the “animalcules” were the ferment itself. "One day he put a drop of liquid undergoing butyric acid fermentation on a glass slide and placed over it a thin glass cover slip. When he observed the flattened drop of liquid under the microscope, he noticed a curious fact. At the center of the drop, the tiny rods were as lively as ever. Around the edges, they had stopped moving.

Now this behavior was very strange! It was exactly opposite to what Pasteur had learned to expect from animalcules when he had studied them in a flattened drop under a glass cover slip. Ordinarily they tried to get close to the edge of the drop where they would find more air.

Create an experiment about spontaneous generation with bouillon and a sealed flask as Pasteur did in Chapter 7. What did you learn from this experiment?

Chapter 6 is a little more challenging. You will see in Chapter 6 that Pasteur tried to help farmers who had suffered from disasters caused by the mysteries of science. In Lille, the sugar beet juice was used to produce alcohol. But sometimes the process failed for unknown reasons. Test Pasteur's experiments with yeast and a lactic acid ferment added to beet juice or a similar material. Is each type of fermentation produced by its own specific type of microorganism or can any microorganism successfully turn beet juice into alcohol? What will happen if two types of microbes are added to the fermentation process or if two types of microbes are present in the fermentation process of beet juice? What is necessary to successfully produce alcohol from beet juice every time? (Chapter 5 has an interesting explanation of the fermentation of wine and will help with understanding Chapter 6.)

At a time when a culture for a dog's urinary tract infection (UTI) can end up with a $300 bill from a lab, it might be interesting to culture a urine sample from a dog in a medium in your school's lab, and see if Rover is sick with the UTI. Or you could use the test to verify the results of the lab that your vet is using.

Obviously, the biography which follows offers many more opportunities to reproduce and learn from the experiments of Louis Pasteur. If you or your teacher have created labs around the work of Pasteur which were interesting, please share them with us at support@ebooksforstudents.org, and we will add them to this page and credit your work. And as you might expect, there are some interesting videos on YouTube related to the experiments above. See an example at https://www.youtube.com/watch?v=FYClCHVT00M

Jim McCabe

support@ebooksforstuents.org

August, 2021

Table of Contents

Publisher's Note about Biology Labs

Prologue

1

The Long Road to the Ecole Normale

2

Explorations in Crystals

3

The First Discovery

4

Pasteur Falls in Love

5

On the Trail of Racemic Acid

6

What Pasteur Found in the Beet Juice

7

The Great Battle Over Spontaneous Generation

8

Life Without Air

9

A New Word for the World-Pasteurization

10

Pasteur Tackles the Silkworm Disease

11

The Riddle of the Corpuscles

12

Pasteur, the Fighter

13

War—and the Search for Jean Baptiste

14

Can Germs Cause Disease?

15

The Conquest of Anthrax Begins

16

The Three Hens

17

The Big Breakthrough

18

Challenge to a Duel

19

Victory at Pouilly le Fort

20

Crowded Years

21

Taming an Invisible Killer—the Rabies Virus

22

How Pasteur Saved the Life of Joseph Meister

23

The Building of the Pasteur Institute

Index

Glossary

AEROBIC BACTERIA—bacteria needing free oxygen to maintain life

ANAEROBIC BACTERIA—bacteria capable of living in the absence of free oxygen

ATTENUATED CULTURE—a culture of microbes whose virulence has been weakened by exposure to air or by some other means

BACILLI—rod-shaped bacteria; plural of BACILLUS BACTERIA—a group of one-celled plant microorganisms, so small they can be seen clearly only with a microscope. Some types bring about certain kinds of fermentations or perform other useful work, some are harmless, and some cause disease; plural of BACTERIUM

BOUILLON—SEE NUTRIENT BOUILLON

COCCI—BALL-SHAPED BACTERIA; plural of coccus

COMPOUND—a chemical substance made up of more than one element

CONTAGIOUS DISEASE—a disease passed from one living thing to another as a result of some contact between them CRYSTAL—a solid body with flat surfaces and angles in a regular, even arrangement

CRYSTALLOGRAPHY—THE STUDY OF THE STRUCTURE AND OTHER CHARACTERISTICS OF CRYSTALS

CULTURE—A CULTIVATED OR SPECIALLY PREPARED GROWTH OF BACTERIA OR OTHER MICROORGANISMS

CULTURE MEDIUM—a liquid or solid substance furnishing food and satisfactory living conditions for the growth of a culture of microorganisms

ELEMENT—the simplest chemical; the basic part of a substance

EPIDEMIC—a rapidly spreading attack of disease affecting many people or other living things

ETIOLOGY—the investigation of the causes of disease

FACET—a little face; one of the small flat surfaces of a crystal

FERMENT—an agent that brings about fermentation

FERMENTATION—the changing of one substance into other substances through the action of certain microorganisms

FIXED VIRUS—a virus of known, stabilized strength

FLACHERIE—a disease of silkworms

GERM—any microorganism; word is most commonly used in referring to disease-producing microbes

GONIOMETER—an instrument for measuring the angles of crystals

HYDROPHOBIA—see RABIES

IMMUNITY—ability of the body to resist the development of a disease

INCUBATOR—IN MICROBIOLOGY, AN OVEN THAT SUPPLIES THE NECESSARY HEAT FOR HATCHING AND GROWING MICROORGANISMS

INFECTIOUS—capable of spreading to others, as an infectious or “catching” disease

INJECTION—the forcing of a fluid (such as a vaccine) into the body through a hollow needle

INOCULATION—the introduction of disease-causing microbes or other substances into the body of a person or animal, either to produce the disease for a research program or to immunize the body against the disease

MEDIUM—SEE CULTURE MEDIUM

MICROBE—any microorganism, but word is most often used in referring to disease-producing microorganisms

MICROORGANISM—a plant or animal so small it can be seen clearly only through a microscope; a microbe

MOLD—a growth formed of yeast or some other kind of microscopic plant

NUTRIENT BOUILLON—a liquid furnishing food and satisfactory living conditions for the growth of a particular type of microorganism

OPTICALLY ACTIVE—having the ability to rotate the plane of polarized light

OPTICALLY INACTIVE—having no effect on the plane of polarized light

PARATARTARIC ACID—ALSO CALLED RACEMIC ACID; a relatively rare form of tartaric acid

PARATARTRATE—one of a group of compounds consisting of paratartaric acid combined with various other chemicals; a salt of the acid

PÉBRINE—a disease of silkworms

PERIOD OF INCUBATION—period of time during which the microbes of a disease are present and multiplying in the body, but before the disease has actively shown itself

PROTOZOA—microorganisms which are tiny, single-celled animals

RABIES—an infectious disease of the central nervous system; also called hydrophobia (when suffered by human beings)

RACEMIC ACID—SEE PARATARTARIC ACID

SEPTIC VIBRIO—a bacterium causing septicemia or blood poisoning

SEPTICEMIA—a diseased condition brought about by the presence of certain bacteria in the blood; blood poisoning

STAPHYLOCOCCUS—any one of a group of bacteria having the shape of a bunch of grapes

STERILIZE—to free from living germs; disinfect

STREPTOCOCCUS—any one of a group of bacteria having the shape of a string of beads

SYMPTOM—any noticeable change or sign in the bodily functions that indicates disease

TARTARIC ACID—an acid obtained chiefly from tartar, deposited in wine casks during the fermentation of grape juice

TARTRATES—any one of a group of compounds consisting of tartaric acid combined with various other chemicals; salts of the acid

VACCINATION—the process of injecting a vaccine into the body

VACCINE—a culture of weakened microbes or similar substance which is introduced into the body to give a very light form of a disease, in order to build up the body’s immunity to a severe form of that disease

VIRULENT—capable of causing death

VIRUS—any one of a group of extremely tiny bodies. With a few exceptions, they are so small they can be seen only with an electron microscope. So far, scientists know only of viruses that cause disease. Viruses can act and multiply only in the living cells of animals, plants, or even microbes. Some scientists classify them not as microorganisms but as particles whose place lies somewhere between living and non-living things

YEAST—a one-celled microscopic plant which brings about alcoholic fermentation; a kind of microorganism

Prologue

ON DECEMBER 27, 1892, distinguished scientists and physicians of France and many other countries assembled in Paris to celebrate the seventieth birthday of Louis Pasteur. Among speakers at the meeting was Sir Joseph Lister, the noted English surgeon, who represented the Royal Societies of London and Edinburgh.

“Monsieur Pasteur,” said Sir Joseph, turning to the frail, white-bearded Frenchman who sat in an armchair on the stage, “truly, there does not exist in the whole world an individual to whom medical science owes more than to you.

“Thanks to you,” Sir Joseph continued, “surgery has undergone a complete revolution which has deprived it of all its terrors, and which has increased its efficacy almost without limit. Medicine is indebted no less than surgery to your profound and philosophic studies. You have raised the veil which for centuries has covered infectious diseases.”

To us today, Lister’s tribute may seem much too sweeping and exaggerated—merely the flowery language of an old-fashioned orator. Nevertheless he meant every word of it.

In Pasteur’s studies of the tiny, almost invisible plants and animals called microbes, Lister had found the key that enabled him to work out antiseptic practices for operations. As a result, the lives of countless surgical patients have been saved because their wounds were protected from infection.

Many of those gathered at Pasteur’s birthday celebration could echo Lister’s words from their own experience. In their laboratories they were tracking down and studying disease-spreading microbes, using methods that had been originated by Pasteur. Thirty-five years before, when he had begun his research on microscopic organisms, they were being investigated only by a few curious botanists and other scientists; most men of science considered them quite unimportant. Pasteur proved their importance, and he developed “microbe farming”—systematic techniques for “raising” a single predominating type of microbe for study or use, in much the same way a farmer raises a pig or a crop of corn. Within a few years the haphazard study of a few microorganisms had grown into a leading branch of science —microbiology.

Some microbiologists in Pasteur’s audience were following still another path that he had pioneered. Instead of curing disease, they were working to prevent it by developing vaccines that would protect men and animals against various deadly ailments.

Strangely enough, the French scientist who was being honored by Lister and others was not himself a physician. By training he was not even a biologist—but a chemist.

As a young man, Pasteur had been so fascinated by crystals that he planned to make them his life work. While still in his twenties, he made important discoveries about the shape of crystals. And he formulated such far-reaching theories concerning them that he is acknowledged to be one of the founders of stereochemistry—the study of the structure of molecules and the three-dimensional arrangement of their atoms.

Later, Pasteur was called on for help in solving scientific problems for French industries. He took on these assignments even when they seemed to be leading him far away from his field. Yet Pasteur made of these apparent detours the road to his greatest discoveries.

In the story of his life we can trace how the research on crystals helped him to solve the mystery of the process of fermentation. This led him to discover the cause and prevention of the diseases of vinegar and wine. From here he passed on to studying the diseases of silkworms and then of animals.

Finally, one day, an appeal from a desperate mother forced Pasteur to take the greatest risk of his career. Into the body of her son, bitten by a mad dog, the scientist injected a powerful vaccine that had never been tested on a human being. The boy’s life was saved—and Pasteur had shown he had found a way to protect people from the terrifying disease known as hydrophobia, or rabies.

Pasteur’s life was full of stormy battles with those who refused to accept his revolutionary theories. Once he was even challenged to a duel! Few scientists have been so violently attacked during their lifetime or—in contrast—so widely honored and loved. It is easy to understand why he has been made the hero of an American motion picture and a French play.

And even now, more than seventy years after Pasteur’s seventieth birthday party, his name is better known throughout the world than that of any other scientist who ever lived. The word pasteurized appears on millions of milk bottles every day; it is in the vocabulary of many languages.

In Brazil, an Institut Pasteur stands on the Avenida Pasteur, one of the most beautiful streets of Rio de Janeiro. In Tunisia, another Institut Pasteur faces on the Place Pasteur of the capital city of Tunis. A hospital in Istanbul, Turkey . . . a garden in Mexico City ... a pharmacy in New York City ... a statue in Chicago, Illinois ... are all named for him. A street in Copenhagen, Denmark, is called Pasteur Vej. Milan, Italy, has its Via Luigi Pasteur.

In scores of other cities of the world, streets and institutes, hospitals and statues still carry the name of Louis Pasteur— chemist and trail-blazing microbiologist, who opened a new era in man’s fight against disease.

1

The Long Road to the Ecole Normale

LOUIS PASTEUR was born on December 27, 1822, in the little town of Dole, in the foothills of the Jura Mountains of eastern France, near the border of Switzerland. His ancestors were humble folk who had lived in the region for hundreds of years. Louis’s great-grandfather, Claude Etienne Pasteur, had been a serf of the Count of Udressier and had bought his own freedom from his master for four pieces of gold.

Louis Pasteur’s father, Jean Joseph Pasteur, was a tanner by trade. Jean Joseph prepared the skins of animals to make smooth, flexible leather. He had been in Napoleon’s army and had been decorated with the Legion of Honor for bravery.

Soon after Louis was born, the family moved to the nearby village of Marnoz. Many years later, when Pasteur had become famous, he was asked to tell the very earliest memory of his boyhood. He said that one day a stranger had appeared in the neighborhood and had started up the mountain road to a village called Aiglepierre. The stranger offered a coin to the child who could first climb the steep road. Louis raced ahead and reached the top far ahead of his playmates.

When Louis was five, his father bought a tannery at Arbois, another town in the Jura foothills. The building, which stood beside the river Cuisance, contained living quarters as well as a workroom and shop.

Louis grew up in Arbois with his father, mother, and three sisters. He loved to fish in the Cuisance; he and his friends knew a secret spot where big trout hid under the rocks. But, in spite of such happy days, he never forgot one terrible time when he was eight years old. A wolf with the frightening disease of rabies ranged across the countryside attacking animals and human beings.

A neighbor of the Pasteur family named Nicole was bitten by the mad wolf. As little Louis watched in horror, a red-hot iron was put on the bites to sear or cauterize them. Nicole’s life was saved—but eight other people died, some of them after much suffering. For years the neighborhood lived in dread of this mad wolf.

In primary school Louis was only an average student. In fact he was considered rather slow because he worked so carefully on an exercise or problem to make sure he had the right answer. He also liked to draw and, when he was thirteen, he made a very realistic portrait of his mother with pastel crayons. Throughout his school days Louis enjoyed making pictures of his family, his friends, the town mayor, and anyone else who caught his eye. A Finnish painter who later studied these drawings commented that they showed talent and that Pasteur might well have had a successful career as an artist.

Monsieur Romanet, the principal of the high school, became interested in Louis and helped him in his studies. With this encouragement, the boy worked hard and became a good student. The principal advised him to aim for the Ecole Normale in Paris, where he could study to become a professor in one of the great universities.

Jean Joseph Pasteur shook his head doubtfully when he heard of this plan. The Ecole Normale was one of the most important schools of France; its entrance examinations were very stiff. Only the best students were admitted there and these had to have a very good preparatory education. The tanner did not have much money to spend on such schooling.

Besides, Louis was only fifteen and Paris was so far away—forty-eight hours by stagecoach! His father argued that the boy could complete his education just as well at the school at Besangon, which was only thirty miles from home. Then he would be prepared to take a position as teacher in the Arbois school. To Jean Joseph, this seemed a fine future for his son.

But Louis’s best friend, Jules Vercel, was going to Paris to study and young Pasteur had his heart set on going there, too. He found new support for his plan when a friend of the Pasteurs, Captain Barbier, arrived in Arbois for a vacation. The captain, an officer in the Paris municipal guard, joined in the family discussion.

“The question of money need not trouble you,” Captain Barbier assured Louis’s father. In Paris, he explained, there was a preparatory school run by a Monsieur Barbet, a native of the Jura region. And the captain added confidently, “Barbet will do for your son what he has done for many other boys from this region—take him at a reduced fee.” Finally Jean Joseph gave his consent.

Louis and Jules left Arbois together on a cold, rainy October morning in 1838. Since there was no room inside their stagecoach, the two boys had to sit on top, huddling under a piece of canvas to keep off the rain and sleet. Even before the square tower of the Arbois church was out of sight, Louis was beginning to wish he had not left home.

His first days in Paris did not improve his spirits. The boy from Arbois was overwhelmed by the noisy, crowded city with its narrow, dirty streets where steep-roofed houses shut out the sun. He was homesick for his family—for the clean mountain air and the sound of the river as it rushed over the rocks near his home—and even for the pungent smell of the tanning pits where the hides were cured. “If I could just get one whiff of the old tannery,” he said longingly to Jules, “then I think I would be all right.”

Monsieur Barbet, the headmaster of the school, worried about the homesick boy and reported the situation to Jean Joseph. One day in November Louis was told, “There is someone here to see you.” It was his father. “I have come to take you home,” said the elder Pasteur simply.

Louis continued his studies at Arbois and later at the school at Besangon. But he did not forget his ambition to attend the Ecole Normale. He worked very hard and by the time he was seventeen, he could write his parents, “I hold a steady place among the best students in my classes, but I hope my standing will be even better within a few months.”

A year later the head of the Besangon school gave young Pasteur a part-time job as supervisor of studies for the younger boys. In this way, he earned his room and board and twenty-five francs a month while still having time to study for his examinations.

In August, 1842, when Pasteur was nineteen, he passed the examinations that made him eligible for the science department of the Ecole Normale. But his class standing— fifteenth among twenty-two candidates—was not good enough to satisfy him. In chemistry he was rated as only “mediocre.” He decided to keep studying until he could be sure of entering as one of the top students. Since he now needed the kind of instruction he could not get at Besangon, it was time to try Paris again. So, once more he made the long trip to the city and the Barbet School.

Monsieur Barbet struck a bargain with Louis. “I will charge you only one-third my usual rate,” the headmaster proposed, “if you will instruct the younger pupils in elementary mathematics each morning, from six to seven o’clock.” Louis agreed, and did such a good job with his pupils that soon Monsieur Barbet did not charge him anything at all.

This time Pasteur was not homesick. He had a good friend in Paris, Charles Chappuis, who had been at school in Besangon and had come to the city to study philosophy. Louis and Charles went once to the opera during the school year and four times to the theater. They saw the greatest French actress of the day, Rachel. “At one time she was applauded more than ten minutes,” Louis wrote home, much impressed. “People clapped and stamped their feet on the floor.”

He was even more thrilled by a different kind of performance. As one of Monsieur Barbet’s students, he was allowed to attend the lectures of the famous chemist, J.B. Dumas, professor at the university of the Sorbonne. Dumas’ lectures were so popular they were always crowded with six or seven hundred students. “I have to go early to get a good seat,” Louis wrote to his family, “just as in the theater.” He and the other students always applauded Dumas enthusiastically. And he would leave the hall excited and eager to discover for himself some of the secrets of the fascinating world of chemistry.

During this period, Pasteur found it hard to concentrate on studying in the room he shared with several other students, so he rented a private room for sixty francs. Since its stone floor made it quite chilly, he rented a stove for eight francs and bought ten francs’ worth of wood for fuel. He paid two francs for a cloth for his table, to cover the holes and cracks that interfered with his writing. With all these expenses, he had to ask his father for an extra hundred francs to finish the year.

Jean Joseph was displeased. He was proud of Louis and anxious to help the boy fulfill his ambitions. But it had been a struggle to keep his son in school and the tanner still was not convinced that all this studying in Paris was necessary for a teaching career.

Louis hastily wrote his father a long letter, explaining that a degree from the Ecole Normale was absolutely necessary to win the kind of professorship he was aiming for. He reminded Jean Joseph Pasteur that for the past three years he had been earning his way, except for incidental expenses. He even outlined where his money had gone in Paris: His four trips to the theater had cost him about two francs each. The opera had cost four francs. Once or twice a week he had dinner with Chappuis at a little restaurant that cost less than two francs. He had also spent twenty francs for music lessons but these he had given up. Otherwise his money had gone for paper, pens, candles, books, and other necessities, including sixty francs for an overcoat.

“If this is too much, I don’t know how to manage,” he wrote. “Nevertheless,” he added respectfully, “you are right to scold me for spending so much. This will make me more economical without hampering me, and I thank you from the bottom of my heart. However, there’s no need to get so upset; you don’t have to be angry with me.”

At the end of the school year, in 1843, Louis again tried for admission to the Ecole Normale. This time he sailed through his examinations triumphantly, winning fourth place on the list of candidates.

2

Explorations in Crystals

LOUIS PASTEUR was so impatient to start on his studies that he arrived at the Ecole Normale several days ahead of time. He got permission to sleep in the big, bare dormitory and, until the rest of the students came, he had it all to himself.

The young man was soon deep in a schedule that kept him busy twelve hours a day. He had seventeen hours of lectures a week, chiefly in chemistry and physics. In addition to classes at his own school, he still regularly attended Dumas’ lectures at the Sorbonne. One afternoon each week he spent in the chemistry laboratory. At another laboratory of his school, he learned such skills as glassblowing and carpentry. He wanted to prepare himself for the time when he would need to make special pieces of apparatus for his own research.

Whenever possible he carried out extra experiments in physics. On Sundays, his one free day, he sometimes persuaded Dumas’ assistant, Barruel, to give him a private lesson in the chemistry laboratory at the Sorbonne. He spent many hours in the library, too, reading biographies of famous scientists and descriptions of their discoveries.

Keeping himself even busier, Pasteur held a class in physical science once a week for Monsieur Barbet’s pupils. This, he felt, was a way to show his gratitude to his former master. And when he returned to Arbois for vacations, he often gave lectures to the students at his old school.

Charles Chappuis sometimes succeeded in dragging Louis away from his books and experiments long enough for a walk and a good visit. But very often Charles found these talks turning to the fields of science that his friend was exploring. The subject that fascinated Louis most was crystallography, the study of crystals and their characteristics. They were still rather a mystery; not much was known about them. But scientists were investigating them because they had learned that crystals could give clues to many puzzling problems in chemistry. Pasteur’s professor of mineralogy, Gabriel Delafosse, had played a part in some important discoveries about crystals while still a student.

However, Louis had little time for crystals; he was much too busy with his courses at the Ecole Normale. After three years he took a competitive examination for a fellowship in physical science. He made fine grades in chemistry and physics but he was not quite so successful in natural history. Still, out of a total of fourteen candidates he was one of four who passed; his rank was third. The examiner said of him, “He will make an excellent professor.”

In France at that time, the next step for a young teacher with Pasteur’s training was usually an appointment by the government to a position at a high school. Louis learned with dismay that he had been assigned to Tournon, a town in southern France where he would have no chance to study for his next goal—a doctor’s degree.

Luckily he had caught the attention of a renowned professor, Antoine Jerome Balard, the discoverer of the element, bromine. Balard was impressed by the hardworking young man who was so enthusiastic about science, and he had already invited Louis to be an assistant in his laboratory at the Ecole Normale. When the great chemist learned of the government’s action, he resolved that Louis should have a chance to finish his studies. Balard used his influence to get the assignment to Tournon canceled.

The post in Balard’s laboratory turned out to be a wonderful opportunity. While Pasteur was preparing for his degree, he could help brilliant chemists with their research projects. He became acquainted with many scientists and discussed the problems they were engaged on. Soon he was being invited to the regular Thursday evening gatherings at the home of Dumas, where he heard more scientific talk.

Best of all, Pasteur now had a laboratory where he could investigate crystals. He set to work to learn the necessary techniques for studying their characteristics, particularly their shape.

Many chemical substances can form crystals but in each substance, the crystals always have their own distinctive form. For example, ordinary table salt is made up of crystals which have the shape of a cube. They are said to be symmetrical. That is, if one of the cubes were cut through the center, the two halves would have exactly the same shape.

Delafosse had studied quartz crystals, which are more complicated in shape than crystals of table salt. They are prisms with six sides and they are said to be asymmetrical. Thus, if a quartz crystal were cut in half, the two halves would have different shapes. One half would have extra faces, or facets, not found on the other half. (See the accompanying sketch.)

Two forms of quartz crystals, showing their irregular facets

Pasteur had heard Delafosse describe the discovery that he and his teacher, Rene Just Haiiy, had made concerning the shape of quartz crystals. They had found that in some of them, the irregular facets are slanted in one direction; in others, the facets are slanted in exactly the opposite direction. In other words, the two kinds of quartz crystals could be called “mirror images” of each other. They are related in shape to each other as are the two gloves in a pair.

Other scientists besides Delafosse and Haiiy had studied these “right-handed” and “left-handed” quartz crystals with an instrument called a polarimeter, which measures the effect of a ray of polarized light passing through a substance. Ordinarily a light wave has a rising and falling motion, similar to that of a wave in water. The polarimeter holds the light wave to a single plane, which might be compared to the surface of still water.

The scientists had discovered that right-handed quartz crystals, when viewed in the polarimeter, twisted, or rotated the plane of polarized light to one side—toward the right. In contrast left-handed quartz crystals rotated light toward the left.

Louis was eager to explore for himself this odd behavior of crystals. Since he could not afford to buy a polarimeter, he built his own. He also made a second instrument called a goniometer, which measures the angles between the facets on crystals. He decided to get some practice with his goniometer by systematically studying one family of crystals.

He chose for his project the crystals of tartaric acid and of a series of nineteen chemical compounds—the tartrates—in which tartaric acid is combined with various other substances. All these crystals have the shape of a prism, like quartz, but they have eight sides instead of only six. Although tartrate crystals are much smaller than those of quartz, they have the advantage of being very easy to crystallize. Pasteur knew that he could get good specimens for examination by dissolving the tartrate compounds in water and evaporating their solutions at room temperature.

He had other reasons for his choice. A French scientist named Frederic de la Provostaye had recently published a thorough study of the series of tartrate crystals. Louis could make his own measurements, then compare his results with de la Provostaye’s report to see how accurate his observations had been. And finally, Pasteur was interested in the tartrates because there was a tantalizing puzzle connected with them which he planned to investigate when he had become a more experienced chemist.

As part of the requirements for his doctor’s degree, he wrote a physics paper which outlined a program of research he planned to make with the polarimeter. By March of 1848, his studies on crystals had advanced to the point where he appeared before the Academy of Sciences to read a portion of a paper he titled, “Research on Dimorphism.” It had been found that certain substances could be made to crystallize in two different forms, depending on the way they were dissolved or melted. Louis made as complete a list as he could of these dimorphous substances. It was quite an honor for the young man to speak before the academy, whose members were the leading scientists of France. He wrote elatedly to Chappuis that his paper had been “very well received” and that several of the members had complimented him on it.

But in that spring of 1848, a patriotic Frenchman like Louis could not give all his thought to crystals. A revolution had broken out in February and Paris was in a turmoil. The unpopular king, Louis Philippe, abdicated and fled to England. Although a republic had been proclaimed, the fighting and rioting continued. The government called for volunteers to keep order.

Pasteur, a strong supporter of the republic, enlisted in the National Guard. He was assigned to help defend the station of the Orleans railway.

One day as he was crossing a square, he saw a wooden scaffolding labeled “Altar of the Fatherland.” A plea for contributions was being made. Without thinking twice the young citizen went home, took all his savings from a drawer and laid them upon the altar.

He was a little uneasy about what his father would say;

he remembered how Jean Joseph had scolded him for spending too much money. But the tanner was patriotic, too—he had not forgotten the days when he had fought for his country. He readily approved of the donation and told Louis to see that it was reported in the Paris newspaper. “Mark it,” he ordered, “‘Gift to the Fatherland: one hundred and fifty francs, by the son of an old soldier whom the Emperor has decorated: Louis Pasteur of the Ecole Normale.’ ”

3

The First Discovery

AT THE BEGINNING of May, Paris quieted down and again and Louis went back to his crystals. He was still working on his tartrate compounds, and still trying to solve that puzzle of the tartrates which had been bothering him ever since he had first read about it three years before.

In the library of the Ecole Normale he had come across a report of some research done by a leading German chemist and crystallographer, Eilhard Mitscherlich. The German had studied two closely related compounds—sodium-ammonium tartrate and sodium-ammonium paratartrate. The first of these compounds is composed of soda, ammonia, and ordinary tartaric acid; the second contains a less common form of tartaric acid which is known as paratartaric or racemic acid.

Mitscherlich had found that his two compounds had the same chemical composition and the same specific gravity. Their crystals seemed to be exactly the same shape, with the same angles. In short, the compounds seemed identical by every test he had made.

Yet when Mitscherlich studied solutions of the two substances in the polarimeter, he could see a big difference in their behavior. The solution of sodium-ammonium tartrate rotated the plane of polarized light toward the right—it was said to be optically active. In contrast the solution of sodium-ammonium paratartrate was optically inactive it had no effect on the plane of polarized light.

Furthermore this same puzzling difference in behavior could be found in all the other tartrate and paratartrate compounds. Solutions of the tartrates, as well as tartaric acid itself, were optically active; the paratartrates and paratartaric acid were optically inactive.

Pasteur turned the puzzle over and over in his mind. Since the two groups of compounds behaved so differently when viewed in the polarimeter, there must be some difference between them—some difference that Mitscherlich had overlooked.

Louis remembered the theory of an English scientist, John Herschel, who had suggested that the optical activity of quartz crystals might be related to their asymmetric shape. Perhaps, thought Pasteur, this was also true of the tartrates. Since they were optically active in solution, it was possible their crystals might be asymmetric.

With this idea in mind, the young chemist made a systematic examination under the microscope of the crystals of tartaric acid and the nineteen tartrate compounds which he had been studying. It was an eye-straining job because the crystals were so small—no larger than grains of granulated sugar.

At length he detected something strange—there were little extra faces on one side of each crystal! They were so very tiny that they had escaped the observation of Frederic de la Provostaye, the French scientist whose study of the tartrates Louis had been using as a model. What was more important—Mitscherlich had missed seeing them, too.

Pasteur felt a flush of triumph. He was right—the tartrate crystals were asymmetric! This might be the clue to Mitscherlich’s puzzle. The young chemist hypothesized:

“The paratartrate compounds, unlike the tartrates, do not show optical activity. Therefore, perhaps the crystals of the paratartrates are symmetric rather than asymmetric—they may not have the little irregular facets I have found on the tartrate crystals. If so, that would clear up everything—it would explain the difference in behavior between Mitscherlich’s two compounds.”

Eagerly Louis prepared the same two compounds Mitscherlich had studied so thoroughly—double tartrate of sodium and ammonium, and the corresponding paratartrate compound—and crystallized their solutions. First, he put the crystals of the tartrate compound under the microscope. Yes—there they were—the little extra facets he had expected to see.

Then he examined the crystals of the paratartrate. As he told the story later, “for an instant, my heart stopped beating” —so great was his disappointment. His hypothesis had been wrong. These crystals, too, had exactly the same irregular little facets he had seen on the tartrate crystals.

Instead of giving up, Pasteur began studying the paratartrate crystals more closely than ever. He turned them around and around under his microscope, examining them from every angle until his eyes ached.

At last his persistence paid off. The crystals were not all alike! In some, the tiny extra facets were on the left side of the prism while in others, they were on the right side. In other words, the paratartrate compound had both right-handed and left-handed crystals, similar to the right- and left-handed crystals of quartz. (See accompanying sketch.)

Right-handed and left-handed crystals of the paratartrate compound which Pasteur investigated.

He had these drawings made to show in accurate detail the tiny facets he discovered.

Pasteur was greatly excited now—maybe he was on the right track after all. With fine tweezers he began to pick up the tiny crystals one by one, painstakingly examining each one under his microscope. The left-handed crystals he put in one pile and the right-handed ones in a second pile.

At this point he was able to formulate several new hypotheses. The first was this one:

“The right-handed crystals which I have obtained from the paratartrate have the same asymmetric shape as the crystals of my tartrate compound. In both kinds of crystals, the extra facets are on the right side. Therefore,” Louis reasoned, “a solution of my right-handed paratartrate crystals should rotate light to the right, the same way my tartrate crystals do.”

He proceeded to dissolve the pile of right-handed crystals —then he examined the solution in the polarimeter. This time, his hypothesis was correct! The solution did rotate light to the right, just as he had expected it would.

Pasteur’s second hypothesis was this:

“The left-handed crystals of my paratartrate compound are the mirror image of the right-handed ones. Therefore, in solution they should rotate light to the left, exactly as far as the right-handed crystals rotated it toward the right.”

He weighed out and dissolved crystals from the second pile, taking care to give this solution the same strength as the previous one. When he viewed his “left-handed” solution in the polarimeter, he found it was behaving exactly as he had predicted it would. His second hypothesis was correct.

Now Pasteur was ready to test his third hypothesis—the most important of all.

He reasoned:

“If I mix a solution of these right-handed crystals with an equally strong solution of the left-handed ones, they should neutralize each other. The mixture would rotate light neither to the right nor to the left. It would be optically inactive.”

His hands were shaking a little with tension as he prepared the two solutions, using exactly the same weight of crystals and the same amount of water for each. Then, holding his breath, he examined the mixture in the polarimeter. Again he was right! It was optically inactive, just like the paratartrate solution Mitscherlich had studied.

Here, at last, was the answer to Mitscherlich’s puzzle.

Solutions of his two compounds behaved differently when seen in the polarimeter because they really were different— the tartrate contained only right-handed crystals while the paratartrate compound contained both left-handed and right-handed ones.

Louis was so excited that he jumped up from his worktable and rushed out of the laboratory. In the hallway he bumped into one of his fellow workers.

“I’ve made a great discovery!” he announced. He grabbed the startled man and pulled him along the hall. “Come on! I must tell you about it!”

In a nearby garden the two men walked up and down, up and down, while Louis poured out the story of the tartrate puzzle and how he had solved it.

At the age of twenty-five Louis Pasteur had, indeed, made an important discovery. His finding that crystals of the tartrates and paratartrates were asymmetric led him to theorize that the molecules of these substances were also asymmetric. And he further theorized that the shape of the crystals of certain substances—such as the tartrates—had a relationship to the shape of their molecules. Through these theories and Pasteur’s later research on the subject of molecular asymmetry, he helped to lay the foundation for the new science of stereochemistry—the study of the shape of molecules and the various patterns in which their atoms are arranged.

Louis immediately announced his discovery at the Academy of Sciences in a paper entitled, “Research on the Relationship That May Exist Between Crystalline Form, Chemical Composition and the Direction of Rotary Polarization.” But he did not have much time to enjoy his achievement. Less than a week later he received word that his mother had had an attack of apoplexy. She died on May 21, 1848, before he could reach Arbois. Her death was such a shock to Louis that he could not think of his studies. He asked for a short leave of absence.

Meanwhile, in Paris, Balard was proudly spreading the word of his pupil’s remarkable discovery among leading scientists. One of the most important of these men proved to be rather skeptical. He was Jean Baptiste Biot, who had discovered that right- and left-handed quartz crystals rotated the plane of polarized light in opposite directions. Biot declared, “I should like to examine closely that young man’s results.”

On Louis’s return to Paris, he made an appointment to see Biot at the College of France, where the older scientist was living. Under the watchful eyes of Biot he repeated his experiment. When the results came out exactly as Pasteur had predicted, Biot took him by the arm and said warmly, “My dear boy, I have loved science so much all my life that this stirs my very heart.”

From that day on, Biot treated Pasteur like a son. He followed attentively each step of the young man’s research and gave him good advice. Moreover he presented a detailed and very favorable report on Louis’s discovery to the Academy of Sciences, emphasizing its importance.

In the autumn Pasteur was appointed a professor of physics in the high school at Dijon. He tried hard to be a good teacher but he was bored and restless because he had no chance for research.

Balard and Biot lost no time pulling strings and using their influence to help him. After three months he was transferred to the university at Strasbourg, where he was made assistant professor of chemistry.

4

Pasteur Falls in Love

LOUIS LIKED the city of Strasbourg and its university. Here he had the laboratory he needed for his crystal studies. And he was welcomed by an old friend from the Ecole Normale, Pierre Augustin Bertin, who was now a professor of physics.

“I have rooms for you in my house,” Bertin announced. “It’s only a few steps from the school.” Pasteur accepted gladly.

As was expected of the new professors, he soon paid a formal call at the home of the rector of his academy. In Monsieur Laurent’s cheerful house, the young Pasteur found an even greater attraction than the school, his laboratory, or his friend, Bertin. The rector had a blue-eyed daughter named Marie. She was twenty-two years old, charming, gentle and gay. Louis promptly fell in love.

Although he wanted to propose to Marie at once, he knew this would never do—it would shock everyone. The correct procedure, in keeping with the French custom of the time, would be to ask his father to come to Strasbourg. The senior Pasteur would then call on Marie’s father and ask for her hand in marriage, for his son.

But Louis was too much in love and too impatient to wait for all this ceremony. Jean Joseph Pasteur was many miles away in Arbois; it might be weeks before he could get to Strasbourg. Suppose—during that time—Marie should become engaged to someone else!

Less than a month after Louis arrived in town, he sat down and wrote a letter to Marie’s father:

“Sir: A request of the highest importance to me and to your family will soon be made to you and I feel it is my duty to furnish you with the following information, which may help decide your acceptance or refusal.

“My father is a tanner in the small town of Arbois in the Jura. My sisters keep house for him and help with the trade. We had the misfortune to lose our mother last May.

“My family is in comfortable circumstances but without fortune. I would not value our possessions at more than fifty thousand francs, and I decided long ago to hand over my share to my sisters. Therefore I have no property at all. My only assets are good health, an honest heart and my position at the university.

“I graduated from the Ecole Normale two years ago, with a fellowship in physical sciences. I have held a doctor’s degree for eighteen months and have presented to the Academy of Sciences some studies which have been very well received.

“This, sir, is my present situation. As to the future, unless my tastes change, I mean to devote myself to chemical research.” He described further his ambitions and prospects and then concluded:

“My father will come to Strasbourg to make a proposal of marriage. No one here knows of my intentions and you may be assured, sir, that if you refuse me, no one will know of it.”

After the proper polite concluding phrases, he added as a postscript, “I was twenty-six last December 27th.” And he enclosed with his letter a copy of the flattering report Biot had written on his crystal discovery.

Jean Joseph duly came to Strasbourg at the end of February. On Sunday evenings Louis went to the receptions given for the professors at the Laurents’ home. Yet the weeks of March drifted by and still the rector gave no response to the proposal. He hardly knew this young man and thought him rather forward.

Louis became more and more uneasy and worried until he finally decided on a new approach. He had noticed that Madame Laurent seemed somewhat more friendly toward him than her husband, so on March 31 he wrote to her, requesting a few private words on the coming Sunday evening. He added:

“I am afraid Mademoiselle Marie may have formed an unfavorable impression of me. I am well aware that there is nothing in me to attract a young girl’s fancy. But experience tells me that when people get to know me well enough, they like me.” He enclosed a respectful note to Marie, which he asked Madame Laurent to pass on to her daughter if she approved of it.

Actually, Pasteur had been too hard on himself. He was not handsome, but he had a pleasant, open face with spectacles covering his gray-green eyes. And Sunday evening brought him the encouragement he wanted—a special smile and handclasp from Marie.

He was rapturously happy and the next day he wrote her again. He still sent the letter through Madame Laurent but this time he addressed her not as “Mademoiselle” but “My dear Marie.”

“Now I have confidence that you will love me,” he wrote. “Thanks, a thousand thanks for your love. I was so restless. I have only one thought: you. My work no longer means anything to me—I, who so much loved my crystals.” He asked for the exact days and hours he might call on her.

Within two months, there was a wedding in the Church of Sainte Madeleine.

Pasteur’s marriage to Marie was one of the luckiest acts of his life. His wife was interested in his studies; she asked him to teach her crystallography so that she could serve as his laboratory assistant. Later on she learned about silkworms, microbes, and vaccines. Louis would dictate his correspondence to her, and she also copied out his scientific papers in her neat, clear handwriting.

Her own letters to her family show that she had a good sense of humor. This was fortunate for her; it was not easy to live with an intense, single-minded genius. And she grew to accept philosophically the fact that her husband worked nights and weekends as well as days when he was deep in a research problem.

Louis and Marie loved each other for forty-six years—until he died with his hand in hers.

5

On the Trail of Racemic Acid

LOUIS AND MARIE Pasteur spent four happy years together in Strasbourg. In April, 1850, a little girl was born, whom they named Jeanne, and in November of the following year they had a son, Jean Baptiste. Biot consented to be the boy’s godfather.

“Louis is a model father,” wrote Marie to Jean Joseph Pasteur. “Even though he’s working hard he finds time each day to cradle his newborn son, and to take care of his daughter when I am busy.”

Louis enjoyed his classes and had time for further studies of crystals. He wrote reports on his findings for the Academy of Sciences, sending his papers first to Biot for criticism.

The wise old scientist gave some good advice on their wording. He objected particularly to Pasteur’s mention of “a result which deserves to attract great attention.” One should never speak so flatteringly of one’s own work, said Biot. It was better to say more simply, “a result which seems to me to offer much of interest.”

Pasteur was growing more and more fascinated by asymmetric crystals and the clues they provided to the shape of molecules. He analyzed a solution of right-handed crystals which he had separated from paratartaric acid and found it was identical with the tartaric acid that chemists were familiar with. In contrast his left-handed crystals in solution formed an entirely new and unknown form of acid—a “left-handed” tartaric acid. To Pasteur, this difference indicated that the molecules of these two acids—as well as their crystals—might be mirror images of each other. And he began to investigate several other acids, to see if he could detect right-handed and left-handed molecules in them.

He worked so hard that Marie became alarmed, fearing that he was injuring his health. But he was not to be stopped, and wrote glowingly to Chappuis, “I am on the verge of mysteries and the veil that covers them is growing thinner and thinner. The nights seem too long but I don’t complain because I prepare my lectures easily and have five full days a week to devote to my laboratory. I am often scolded by Madame Pasteur but I console her by telling her that I shall lead her to fame.”

One thing bothered him—he had trouble finding the supplies of paratartaric acid that he needed for his research. For some reason the acid had become very scarce in recent years. Unfortunately no one knew how to make it or what caused it to form. Other chemists besides Pasteur were interested in studying it, and the Paris Pharmaceutical Society had offered a prize of fifteen hundred francs to anyone who could produce it synthetically.

This elusive substance had been first discovered in 1820 by Kestner, an Alsatian manufacturer of tartaric acid. Tartaric acid was obtained from tartar, which collected as a thick crust on the inside of wine vats during fermentation. Kestner had noticed odd little tufts of crystals appearing occasionally among the ordinary tartaric acid crystals he was producing. The new substance, called paratartaric acid, had also been named racemic acid, from the Latin word for “cluster of grapes.”

After Kestner’s discovery, other manufacturers of tartaric acid sometimes spotted a few racemic acid crystals in their product. Then suddenly they ceased to appear. Not even Kestner could find them in his vats. This state of affairs was very frustrating for research chemists like Pasteur.

He first found the trail of the missing racemic acid in August, 1852, during a trip to Paris. Biot invited his young friend to meet Mitscherlich, the German chemist who had first posed the tartrate puzzle that Louis had solved. At Biot’s suggestion, Pasteur brought along his left-handed and right-handed crystals and gave a two-hour demonstration before the friendly and interested German scientist. Louis was delighted with the meeting and the best part of it was some news that Mitscherlich had for him—a certain German manufacturer was said to be producing racemic acid once again.

“I’ll go to Germany,” Pasteur decided immediately. “I must discover the source of racemic acid.”

The trip would cost at least a thousand francs—a huge sum for a young husband and father who earned only 2,750 francs a year. He begged Biot and Dumas to get the money for him from the government or the Academy of Sciences. He even considered applying directly to the President of the Republic.

Pasteur’s friends promised to help—if he would just have a little patience. But when he received Mitscherlich’s letter of introduction to the German manufacturer, he felt he could not wait another minute for the red tape to unwind. He scraped together what funds he could borrow and set out, trusting that the grant would come through and Marie could forward him enough money for the return trip.

He went first to the German town of Zwickau, where Mitscherlich’s manufacturer of tartaric acid had his factory. There Pasteur was disappointed to learn that Mitscherlich had been mistaken; the manufacturer was finding so little racemic acid in his vats that he did not bother to save it. But he gave his French visitor samples of the two kinds of tartars he used—one of which he imported from Austria and the other from Italy. Furthermore he offered a bit of information that made Pasteur prick up his ears. Some years before, the German explained, he had found sizable amounts of racemic acid in his vats—and at that time, his tartars h,ad come from Trieste.

Obviously the next step for Pasteur was to locate the source of the different tartars. From Zwickau he went to the German city of Freiberg, where he investigated more tartaric acid factories. From there he followed the trail to Vienna, then on to Prague, like a man tracking down clues in a treasure hunt. He visited manufacturers of tartaric acid and refiners of crude tartar. Wherever he went he “borrowed” laboratories to analyze samples of the substances.

Pasteur had intended to go as far as Trieste in his search but this proved to be unnecessary—by the time he reached Prague, he had pieced together the solution of the mystery. In the first place, he learned that the source of the tartars was an important factor, since tartars originating in different regions varied widely in the amount of racemic acid they contained.

But his most valuable finding was confirmation for a suspicion he had formed even before he left Strasbourg. Many manufacturers who had formerly used crude tartars had now switched to tartars that had already passed through one refining process. During the refining, the part of the tartar that contained most of the racemic acid was thrown away. Thus it was no wonder that the acid had disappeared from Europe.

While in Prague, the traveler visited a chemist who claimed to have produced racemic acid synthetically from tartaric acid. Pasteur soon found that the man was mistaken but the experience fired Louis himself with a new ambition. He would find a way to transform pure tartaric acid into racemic acid.

Back again in his own laboratory, he worked on the problem all winter and by the following May he had solved it. His method was to keep one of the tartrate compounds, cinchonine tartrate, at a high temperature for several hours. When he crystallized his synthetic racemic acid, it contained right- and left-handed crystals, exactly like the crystals of naturally formed racemic acid.

This feat won Pasteur new recognition. In August, 1853, he was made a chevalier of the Legion of Honor and, in November, the Paris Pharmaceutical Society awarded him its fifteen-hundred-franc prize. The money was particularly welcome to the Pasteurs because their family was still growing. A third child, Cecile, had been born just the month before.

However, the earnest young scientist could spare only half the prize money for his family expenses. The other half was spent on equipment for new research projects—apparatus Pasteur had not been able to afford on his small laboratory allowance from the government.

Gradually his imaginative mind had been carrying him into a bold new line of speculation. From the theory that the shape of certain crystals had a relation to the shape of their molecules, he had advanced to an even more startling idea. The shape of molecules, he thought, might be the key to the difference between living and nonliving things.

Among the substances Pasteur regarded as living things, he included the tartrates, which had their origin in the tartar formed from grapes. As he had discovered, the tartrates had asymmetric crystals which were optically active in solution. And as his friend, Biot, had discovered some years earlier, certain other substances—including sugar, camphor, and turpentine—were optically active in the liquid state and in solution.

Quartz was different. Its crystals were asymmetric and optically active but when these were dissolved, the solution proved to be optically active. Pasteur believed this indicated that the quartz molecules themselves must be symmetric rather than asymmetric.

On the basis of these facts and theories, he drew a tentative generalization: Substances which came from living things—such as the tartrates, sugar, and camphor—were composed of asymmetric molecules. Nonliving things—such as quartz—were composed of symmetric molecules.

Pasteur was not content with merely theorizing. He became ambitious to transform the symmetric molecules of a substance into asymmetric molecules—thus changing a nonliving substance into a living one! This was a big order—as Pasteur knew very well. In his attempt to bring about such a transformation, he experimented with various devices. For instance, he used very powerful magnets to try to introduce asymmetric influences during the formation of crystals.

But the results of months of such experimentation were discouraging. “My studies are going badly,” he wrote to his father at the end of 1853, adding ruefully, “One has to be a bit crazy to undertake what I have undertaken.” Pasteur eventually turned away from this line of research, although in future years he went back several times to his crystal studies. And it was a long time before he finally gave up his dream of transforming a nonliving substance into a living one.

Even today, more than one hundred years later, scientists are still struggling with the problem of synthesizing living matter. They have learned that Pasteur was on the right track in finding a relationship between optical activity and life— but the distinction between living and nonliving things is rather more complicated than he believed it to be.

In spite of Marie’s chidings, he did seriously overwork himself and, early in 1854, he was granted a leave of absence for his health, fortunately with pay. He and his family rented rooms in Paris, where Louis took advantage of the chance to do some experiments with Biot and to attend Dumas’ lectures, seeking pointers for his own teaching.

By autumn Pasteur had fully recovered and he was appointed professor of chemistry and dean of the newly organized faculty of sciences at Lille. He went on ahead to his new post, leaving Marie to follow with the three children.

As dean, he was expected to make a speech at the school’s opening ceremonies. Louis dreaded the task; he had always been timid about addressing big audiences. But his speech was such a success that he wrote Marie the same day, “Large meetings no longer scare me; instead, they stimulate me.” During his speech Louis Pasteur used one sentence that was to prove true in his own life again and again. In the fields of scientific observation, he said, “Chance favors only the mind that is prepared.”

6

What Pasteur Found in the Beet Juice

LOUIS CONTINUES to work with enthusiasm. He is up to his neck now in beet juice,” Madame Pasteur wrote to her parents from Lille in December, 1856.

Six weeks earlier, a Monsieur Bigo, the father of one of Pasteur’s students, had come to him with a problem. Bigo manufactured alcohol from sugar beets. Recently his beet juice had been spoiling instead of turning into alcohol properly.

“Can you tell me what is wrong?” he asked.

Pasteur promised to investigate. He knew it was his duty; the government had issued an order that all science professors in the universities should use their knowledge, whenever possible, to help French industries. And the raising and processing of sugar beets was one of the most important industries of the Lille region.

He had another good reason for tackling Bigo’s problem. It fitted in with a mystery of science that Pasteur was becoming more and more curious about—the cause of the process of fermentation.

For a while the chemistry professor visited Bigo’s factory almost daily. He poked about among the big vats where the beet juice was kept and watched every step of the manufacturing process.

To make alcohol, the workers added to a vat of fresh juice a small amount of a yellowish substance—yeast. Gradually the yeast spread to form a mold. Little bubbles appeared in the juice and it was then said to be fermenting.

When fermentation was “healthy,” the sugar in the beet juice was gradually changed into alcohol. But sometimes the fermenting juice turned into a sour, spoiled liquid that Bigo had to throw away.

Pasteur collected samples of the juice, as well as the thick deposits in the vats. He took them to his laboratory where he had a low-powered student’s microscope. After studying scores of samples, he began to detect a slight difference between them.

In healthy juice, where fermentation was proceeding properly, he could see small round globules which he recognized as yeast cells. In the spoiled juice, he noticed globules that were oblong and much smaller.

He told Bigo, “Keep a check on your beet juice with a microscope. When the globules are round, your juice will ferment successfully. But if you see oblong globules, throw out the juice. It’s going to spoil.”

“When you start a new fermentation,” Pasteur warned, “be sure to add the round yeast globules—keep out the little oblong ones. Then your fermentation will be healthy.”

This advice cleared up Bigo’s trouble. But Pasteur’s study of the little globules had made him more eager than ever to investigate the questions that were then puzzling scientists :

Why and how does fermentation bring about the changing of beet juice into alcohol—and of grape juice into wine?

Why does milk ferment and turn sour?

How is fermentation related to the process of putrefaction—the spoiling and decay of meat, eggs, and other foods ?

By 1856, scientists had made some progress in analyzing what took place chemically during these changes. For instance, they had learned that the bubbling in fermenting beet juice was caused as carbon dioxide gas formed along with the alcohol and escaped into the air.

In addition to the process of alcoholic fermentation—in which sugar is changed into alcohol—the scientists had studied several other types of fermentation. Lactic acid fermentation, they discovered, took place when milk soured and the sugar in it changed into lactic acid. Acetic acid fermentation occurred as wine or cider changed into vinegar. Putrefaction was usually considered still another kind of fermentation.

But what brought about these fermentations? On this point there was much confusion and disagreement.

“Fermentation is simply a chemical change,” said the most influential chemists of the day. “When beet juice ferments, the molecules of sugar are broken down and their atoms rearranged to form new kinds of molecules—chiefly those of alcohol. During putrefaction the molecules in rotting meat are broken down and their atoms are rearranged in somewhat the same way.”

“No, fermentation is brought about by living agents,” a few scientists suggested. “The living agent in alcoholic fermentation is yeast.” These scientists tried to carry out experiments supporting their claim but the experiments sometimes failed and their theory of “live” yeast was ridiculed by most authorities.

Some chemists said that yeast was merely a catalyst, a chemical substance that brought about alcoholic fermentation without actually becoming a part of the process. Still another view was held by Justus von Liebig, a very famous German chemist. Liebig admitted, “It is possible that yeast may once have been a living thing, a microscopic plant, If so, when fermentation takes place it is dead and its molecules are breaking down and vibrating. This vibration helps break down the sugar molecules to form alcohol and carbon dioxide.”

Pasteur sided with the few scientists who believed that fermentation was brought about by a living thing of some kind. He was led to this belief in a roundabout way, through his study of crystals and his work with the polarimeter.

During his first year in Lille, he had made a thorough study of amyl alcohol. This chemical substance was produced in small amounts during fermentation and had rather complicated molecules compared with some more common kinds of alcohol. When Pasteur observed one form of amyl alcohol in the polarimeter, he could see that it was optically active. According to the theory he had developed while at Strasbourg, optical activity in a liquid indicated that its molecules were asymmetric, a characteristic that distinguished living things from nonliving things. Therefore, he told himself, the fermentation that produced amyl alcohol must somehow be a process involving life—not just chemical change.

Said Liebig, “Naturally amyl alcohol is optically active. It is derived from sugar—and sugar itself is optically active.”

This explanation did not satisfy Pasteur. He reasoned, “The complicated molecules of amyl alcohol are very different from sugar molecules. They would have lost their optical activity during fermentation unless—as I believe— fermentation itself is due to living agents.”

His belief was so vague and had so little evidence to support it that he did not even consider it a working hypothesis. He referred to it as a “preconceived idea.” In later years, Pasteur was to have many other preconceived ideas. Some of them led to his most brilliant discoveries. Others proved to be contrary to the facts he developed by experimentation. In these latter cases he was deeply disappointed but he never hesitated to discard the idea at once.

Pasteur now set to work in his laboratory to see if he could find evidence of the living agents of fermentation. He had to do his research at odd moments since he was busy with classes and his duties as dean. Luckily the laboratory was right beneath his apartment. He could work late at night and keep a continuous check on his experiments.

He made a special study of the round yeast cells which he believed were the living agents causing alcoholic fermentation. When he put a few of the globules in a solution containing sugar, the mixture began to ferment and the sugar was changed into alcohol. Pasteur also watched the yeast globules reproduce themselves by the process called budding. A little lump, or bud, would form on a “mother” globule, grow to full size, break free, and then begin to develop a bud of its own.

But other scientists, too, had seen and reported the budding of yeast cells; Liebig and his fellow chemists had not been impressed. Liebig had argued, “If yeast is necessary to produce fermentation, how can you explain the fact that it is not needed in other types of fermentation besides alcoholic fermentation? Consider the production of lactic acid, for example. Nothing resembling yeast is present during that fermentation.”

Pasteur thought, “Suppose I could prove that a living agent—something like yeast—brought about lactic acid fermentation. That would knock out one of Liebig’s strongest arguments.”

Chemists already knew a way to bring about a lactic acid fermentation. If they put a little chalk and some albumin or other nitrogenous material into sugared water, the sugar was gradually changed into lactic acid. They suggested various and often conflicting reasons for this change, but Pasteur thought he had the right answer.

His research on beet juice had given him the key. In making a chemical analysis of the juice as it turned sour, he had discovered that a lactic acid fermentation was taking place. Pasteur suspected the fermentation was brought about by the tiny oblong globules he had found in the thick substance of the spoiled juice. A similar gray, clotted substance, formed mostly of nitrogenous material, appeared during the souring of milk and in other lactic acid fermentations.

In this thick, clotted deposit, it was difficult and sometimes impossible to distinguish the tiny oblong bodies. No wonder observers had not noticed them before! But Pasteur’s sharp eyes had caught them—and he believed they were alive. He set out to find a way to grow the oblong globules so he could study them.

He concocted a clear “soup” for them—what we now call a nutrient bouillon. In his “recipe” he used the ingredients that had seemed to be favorable for a lactic acid fermentation—nitrogenous material, chalk, and sugar. To make his bouillon, he first poured boiling water on brewers’ yeast and let this mixture stand for a while at a temperature of 1oo°C. (2i2°F.). Part of the protein and mineral matter of the yeast became dissolved in the water, supplying the nitrogenous material he needed. Then he filtered out and discarded the solid part of the yeast, leaving a clear liquid into which he dissolved some sugar.

Pasteur put some of this nutrient bouillon (called “sugared yeast water”) into a flask and added to it a little chalk and a bit of the thick gray stuff from a lactic acid fermentation. He set the flask in an oven at 30°C. to 35°C. (86°F. to 95°F.) and left it there overnight.

Early the next morning he hurried downstairs to inspect his flask. Something was happening in it! The clear liquid had become cloudy and was bubbling gently. Clots of a gray substance were beginning to form on the glass sides of the flask. And when Pasteur examined this substance under the microscope, he found in it the same kind of little microscopic oblongs he had spotted before.

He sowed a few of the oblong globules in a flask of sugared yeast water. Lactic acid began to form, but rather slowly and weakly. When he added a little chalk there was a much livelier fermentation; the globules multiplied and lactic acid was formed more rapidly. After performing the same experiment many times, Pasteur came to this tentative conclusion: “The chalk neutralizes the liquid, and the little globules evidently prefer a neutral bouillon to an acid or alkaline one.”

As for the brewers’ yeast—he believed that its protein and mineral matter simply served as food for the globules. Any stray yeast cells that managed to slip through the filter into his bouillon were sure to be dead ones, killed by the boiling water. He tested this belief by experimenting with other recipes for his bouillon, substituting other kinds of nitrogenous matter for the filtered yeast extract. The globules grew successfully in some of these substitute bouillons, too.

Working night after night in his laboratory, Pasteur carried out hundreds of experiments while his patient wife waited upstairs. He tried to grow his lactic acid globules under all sorts of conditions. He experimented, too, with alcoholic fermentation and other types of ferments.

During the winter and spring of 1857, the young professor occasionally lectured to his students and to the Lille Scientific Society on some of his findings concerning the chemical changes that took place during various fermentations. But he did not yet dare to say he thought his ferments were alive.

Finally, on August 3rd, Pasteur gave a detailed report on his lactic acid research before the Lille Society. Choosing his words very carefully, he reminded his audience that an alcoholic ferment, yeast, is to be found wherever sugar breaks down into alcohol and carbonic acid. In the same way, he explained, “there is a specific ferment, a lactic yeast, which is always present when sugar turns into lactic acid.” (Later he recognized that the ferment he called “lactic yeast” was actually a species of bacteria.)

And still he avoided saying flatly that the little oblong globules were living things which produced lactic acid. He stated cautiously, “Throughout this paper I have reasoned on the basis of the hypothesis that the new yeast is organized, that it is a living thing, and that its chemical action on sugar corresponds to its development and its organization.”

Although Pasteur did not mention Liebig’s name in his paper, he was clearly contradicting that celebrated chemist in his further statement that “fermentation appears to be correlative to life and to the organization of globules, and not to their death or putrefaction.” Pasteur was frank to admit, however, that he was following a line of thought “which, strictly speaking, could not be irrefutably demonstrated.” Not until years later did he develop experiments which backed up his hypothesis with solid proof.

Four months later he published a second paper, dealing with his research on live yeast globules as the agent in alcoholic fermentation. These two papers did not make much of a stir in 1857 and they did not convince Liebig and his fellow chemists. Nevertheless, they are considered milestones in the history of microbiology.

“With Pasteur began the domestication of microbial life,” Dr. Rene J. Dubos, a leading American scientist, has written. Pasteur showed how a “wild” microorganism could be tamed and made to work more efficiently—in bringing about a fermentation, for example. Its growth could be controlled; it could be encouraged or discouraged, according to the treatment it was given. If a certain kind of microorganism were placed in the right nutrient bouillon, which gave it the right kind of food and living conditions, it would grow and reproduce many microorganisms just like itself. These microscopic “children” would carry on the same type of life and activity as their parents.

Moreover, Pasteur learned that different microorganisms had widely differing preferences as to food and living conditions. Some kinds had very special requirements in food and some were more fussy than others about the temperature. Also, some microorganisms—such as those producing lactic acid—grew best in a neutral bouillon. Other types preferred an acid or an alkaline bouillon. If a microorganism were put in an acid bouillon when it preferred an alkaline one, its growth and reproduction might be slowed down or stopped altogether.

Before Pasteur’s day, scientists had believed that one kind of fermentation might be transformed into another kind. For instance, they thought lactic acid and acetic acid ferments were products of alcoholic fermentation. But Pasteur showed that this theory was not correct—each kind of fermentation is produced only by its own specific kind of microorganism.

You did not need to sow a ferment, he also pointed out. It could appear spontaneously, as a weed springs up in a plowed field. Sometimes several kinds of ferment might appear in the same liquid. “One might compare what happens in fermentations,” Pasteur explained, “to the soil in which nothing is planted. It is soon choked with plants and insects of various kinds.”

If you wanted to grow one particular ferment in the “field,” it helped to sow some of that ferment so it would have a good head start. With favorable living conditions, your ferment might choke out most of the “weeds”—those uninvited microorganisms that managed to slip in. For example, Pasteur had shown Bigo how to make sure he was sowing yeast globules—not a lactic acid ferment—in his beet juice. With a healthy yeast ferment under way, it was not so serious if a few lactic acid microorganisms slipped in.

One of Pasteur’s goals was to develop techniques for growing a single kind of microorganism by keeping out or killing all the other microscopic plants and animals. A single kind of microorganism growing in a nutrient bouillon is known as a pure culture.

Another experiment which Pasteur carried out during this period at Lille impressed him deeply because it formed a bridge between his studies on crystals and fermentation. Late in August, several weeks after presenting his first re-port on lactic acid fermentation, he happened to notice a tartrate solution that had been standing for some time in his laboratory. It was beginning to ferment; a mold was forming on it. Pasteur guessed that this mold must be the fermenting agent, which had somehow gotten into the liquid.

Immediately Pasteur’s active mind thought of an interesting problem. Could he bring about a similar fermentation in a solution of a paratartrate—one of those compounds which he had discovered would form right-handed and left-handed crystals ?

He sowed a bit of the mold in a paratartrate solution and found out that it did, indeed, ferment. Furthermore, when he examined some of the fermenting liquid in the polarimeter, he was amazed to discover that this paratartrate solution—ordinarily optically inactive—was gradually becoming optically active. As fermentation continued, Pasteur kept checking samples of the liquid in the polarimeter and he saw that the fermenting liquid was causing the plane of polarized light to rotate more and more toward the left.

When fermentation had stopped, he crystallized the liquid. Examining the crystals under his microscope, he discovered they were all left-handed ones—all of the right-handed crystals had disappeared! Apparently the ferment had chosen to “feed” only on the right-handed tartaric acid in the solution.

A page from one of Pasteurs laboratory notebooks, during his early fermentation research. He has drawn and minutely described some of the yeasts and mold spores he studied with his low-powered microscope. Although his drawing is crude, it is so accurate that modern microbiologists can identify the organisms Pasteur saw.

This surprising result—in which a ferment changed an optically inactive solution into an optically active one—made Pasteur more convinced than ever that yeast and other fermenting agents must be living things.

In later years, as scientists dug still deeper in their investigations of fermentation, they learned that while Pasteur was right in calling his ferments living organisms, there was also truth in the theory that fermentation was brought about by chemical substances—catalysts. In 1896 a German chemist, Eduard Buchner, isolated such a chemical in yeast. His research showed that the little yeast plant itself manufactured this catalyst—one of the group of chemical substances which are produced by living cells and which are called enzymes.

Two months after Louis Pasteur presented his lactic acid report, he returned to Paris as director of scientific studies and administrator at his old school, the Ecole Normale.

“Our faculty loses a professor and a scientist of the very first order,” the rector at the Lille university said of him. During Pasteur’s three years at the school, he had built up the science department and brought in fresh teaching ideas. One of his innovations was the planning of student field trips to factories, steel mills, and metalworks—a practice almost unheard of at that time.

Another important honor had come to him during his last year at Lille—the Royal Society of London awarded him its Rumford Medal for his discoveries in crystallography. Scientists outside France were beginning to take notice of the accomplishments of this young French chemist. For Pasteur was not yet thirty-five.

7

The Great Battle Over Spontaneous Generation

IN PARIS the Pasteurs settled into a pleasant apartment at the Ecole Normale. It was to be their home for the next thirty-one years.

Pasteur no longer had a convenient laboratory underneath his home—in fact, he had no laboratory at all. The school authorities expected him to be an administrator rather than a science professor. They saw little reason to give him a place for performing experiments.

But this did not stop Pasteur from planning a laboratory on his own. He explored the school building and found two tiny attic rooms that were empty because no one wanted them. He cleaned out the dust and the cobwebs and moved in with his test tubes and flasks.

Since he had no assistant, he swept out the lab and washed his own utensils. When Marie had time, she climbed the five flights up to his attic to help him.

Pasteur was perfectly willing to carry on his experiments chiefly in his spare time. The big problem was finding money for chemicals and equipment. Often he paid for these out of his own pocket, keeping the receipts in the hope that he would get the money back one way or another. Usually he managed to be repaid—but not always. He swallowed his pride and begged for funds from committees of the Academy of Sciences and from various government departments— sometimes getting turned down. Whenever he won a prize for a piece of research, at least part of the money usually went for lab expenses. For years he financed his laboratory in this uncertain way.

In spite of these difficulties, Pasteur enjoyed his life at the school. He and Marie held open house on Sunday afternoons for friends, faculty members, and students. They kept up their custom of entertaining on Sundays through much of their life together.

In July of 1858, a little girl was born, bringing their family to three girls and one boy. They named the new arrival Marie Louise.

Pasteur handled his administrative job conscientiously, even to such details as checking on the amount of meat each pupil was served at a meal and seeing that the courtyard was strewn with sand. And he still found time to carry out new experiments on different types of fermentations, reporting his findings regularly to the Academy of Sciences.

He did his best to plug every loophole in his work. For example, he knew that his opponents would say that fermentation was brought about in his flasks not by living organisms but by the chemical breaking-up of the once-living matter— the filtered yeast extract and other nitrogenous material —that Pasteur put into his nutrient bouillon to serve as food. To meet this argument, he labored to concoct a bouillon that would contain only mineral salts as food for his ferment. After many failures he did succeed in this attempt, and he proved that yeast would ferment sugar to form alcohol even in a purely mineral nutrient bouillon.

During his second year at the Ecole Normale, he began one of the hottest battles of his career—the great debate on the doctrine of spontaneous generation. To win it, he would travel from the deepest cellar of the Paris Observatory to a mountaintop of the Alps.

It was a battle Pasteur knew he would have to fight sooner or later. He had advanced the startling idea that living, microscopic bodies brought about different kinds of fermentation. He suspected that they caused putrefaction, too.

But where did these microorganisms come from? Everyone knew that milk soured when it was left standing; you did not need to sow a lactic acid ferment in it. According to Pasteur’s theory, living yeast globules fermented the sugar in grape juice to form the alcohol in wine. Yet no one had to put yeast in the juice. It just appeared somehow at the time the grapes were harvested.

Some scientists declared, “The microorganisms that appear during fermentation and putrefaction are produced by spontaneous generation. They have no parents. They are formed spontaneously from the fermenting or decaying material itself. Molecules of food and other living substances break up during fermentation and rotting. Their atoms rearrange themselves into new molecules that make up new living things—the microorganisms.”

The doctrine of spontaneous generation was thousands of years old. It had been used by men to explain the sudden appearance of living things they could not account for in any other way. Even in the seventeenth century a respected physician, Jan Baptista van Helmont, declared that mice could be created by putting together some old rags and a piece of cheese. Eels were thought to be spontaneously generated from mud and worms from rotting meat.

By the eighteenth century scientists had studied mice, eels, and worms closely enough to see that these creatures had parents and children like themselves. Some investigators claimed that even bacteria and other microorganisms had parents. They tried to prove it but their experiments did not convince the believers in spontaneous generation.

In Pasteur’s time a leading advocate of the doctrine was Felix Archimede Pouchet, director of the Natural History Museum of Rouen. In December, 1858, he reported to the Academy of Sciences on a series of experiments he had made. He titled his paper, “A Note on Plant and Animal Protoorganisms Spontaneously Generated in Artificial Air and in Oxygen Gas.”

Pasteur snorted a bit when he read a copy of Pouchet’s report. He heavily underlined certain statements which he meant to check with experiments when he had the time for it. But Pouchet did not wait to hear from Pasteur; he realized the chemist’s studies on fermentation were a threat to his doctrine. He wrote challenging Pasteur to state his views.

Pasteur replied politely, “The experiments I have made on this subject are too few and, I must admit, too variable in results for me to dare have an opinion worthy of being communicated to you.” He told Pouchet frankly that he was not convinced by the naturalist’s experiments, which he felt were “not founded on facts of irreproachable accuracy.” And he added, “I think you are wrong, not in believing in spontaneous generation (for it is difficult in such a case not to have a preconceived idea) but in affirming so positively that it exists. In experimental science it is always a mistake not to doubt when the facts do not compel affirmation. ... In my opinion the question is open and untouched by decisive proofs.”

His own study of the question had to be postponed because he was too busy with other work. Then, during the summer the Pasteurs had a family crisis. Their daughter Jeanne became sick while at her grandfather’s house in Arbois. Marie went to Arbois to nurse the little girl, leaving Louis in Paris to keep an eye on the younger children. Laboratory experiments had to wait while Pasteur entertained his charges. He even took seven-year-old Jean Baptiste to see a play called “Edward’s Children.” The boy had a wonderful time; he laughed so hard and asked so many questions that everyone around them laughed, too, rather embarrassing his father.

Pasteur waited anxiously for news from Arbois about Jeanne. At first she seemed to be recovering—then she grew steadily worse. The doctors tried their best to save her, but they had no real knowledge of what caused her illness or how to fight it successfully. She died early in September of 1859.

Pasteur wrote bitterly to a friend, “Our dear little eldest daughter, life and health itself, has been taken from us by that frightful disease that they call typhoid fever. For them, for their feeble 'science,’ it is only a word.”

In the autumn of 1859, he finally had a chance to start on spontaneous generation experiments. He had managed to get a new laboratory during the year, a small building on the school grounds. It was rather cramped; he had to install under a stairway the incubator he needed for his flasks of microorganisms. To reach the oven door Pasteur was forced to crawl on his hands and knees. But it was better than the attic and, best of all, he was even given a laboratory assistant.

The little building was soon stuffed with complicated equipment that he had invented for various projects. He developed dozens of different kinds of experiments but the following are the principal ones, with the reasoning that led up to them.

Pasteur hypothesized, “Many microorganisms are floating in the air. They drop on food and other living substances, grow and multiply, and bring about such changes as fermentation and putrefaction.”

Accordingly his first task was to find out whether or not microorganisms were in the air.

First he plugged a glass tube with a wad of guncotton, then used an instrument to suck air in through the tube. The cotton plug acted as a filter to catch dust and other particles that had been floating in the air. After twenty-four hours the cotton became gray with these particles.

Next, he took out the cotton plug and dissolved it in a test tube containing alcohol and ether. A residue settled to the bottom. When Pasteur examined this under the microscope, he saw many little round and oval globules mixed in with the dust. They looked just like the tiny organisms he had often studied under his microscope. Of course this did not prove they were living things. Even if they had once been alive, the alcohol and ether mixture had killed them.

Pasteur now decided to see if he could grow the airborne globules in a nutrient bouillon, as he had done with his ferments. He filled a flask half full of sugared yeast water, being careful to make it sterile. Even the air in the flask was passed through a red-hot tube to kill any microorganisms in it. Then he quickly sealed the neck of the glass flask with a flame.

As long as this flask was kept sealed, no microorganisms appeared “spontaneously” in it—even when Pasteur left it in the incubator for many weeks to encourage their growth. But as soon as he broke the seal to let in the air, a big change could be seen in the bouillon within a day or two. The clear liquid grew cloudy and tufts of silky threads began to appear. Examining a drop of the liquid under the microscope, he discovered that the cloudy effect was caused by swarms of bacteria. The silky threads were molds and other microorganisms of different kinds.

Pasteur next tried slipping into his sterile yeast water one of the cotton plugs on which he had collected particles from the air. He used a complicated tube-within-a-tube device to keep all microorganisms out of the flask except those on the plug itself. Then he crawled in under his stairway to put the flask in his incubator, making a note of the time —9 :oo A.M.

At nine the next morning he wriggled in again to inspect his flask; there was no change in the clear liquid. Yet by six o’clock the same evening, he saw with elation that little tufts of mold were beginning to sprout from the dusty plug. In the next two days he made dozens of trips on his hands and knees to the door of that inconvenient incubator, to watch his flask as the mold spread and the liquid grew cloudy with bacteria.

Many times he repeated his experiments with the dust-covered cotton plugs, getting plenty of exercise on the way to the incubator. Each time the sugared yeast water became filled with microscopic things that grew and multiplied, although he noticed that the types of microorganisms varied in each flask. He tried other kinds of nutrient bouillons with similar success.

This elaborate apparatus was built by Pasteur so that a little cotton plug {arrow), on which microorganisms had been trapped, could be slipped into the sterile flask at the right while microorganisms floating in the air were kept out.

Pasteur now felt he was collecting pretty good evidence that the air contained living organisms which could reproduce themselves—if they were given the right food and living conditions.

He knew that Pouchet would probably offer the objection, “Cotton itself comes from a living plant. That explains why living organisms can be formed from it.” So Pasteur repeated his experiments using a mineral substance—asbestos —to catch the particles in the air. His results were exactly the same as with the cotton plug.

Some plugs were prepared as controls, to check these results. For example, Pasteur sterilized a wad of asbestos and, without collecting dust on it, slipped it carefully into a flask of yeast water. Into other flasks he put dust-laden plugs which he had sterilized to kill their microorganisms. In both of these experiments, the yeast water stayed clear no matter how long the plugs remained in it.

Still, Pasteur was not ready to confront Pouchet; there was another objection that might be raised to his experiments. Many believers in spontaneous generation claimed that ordinary air, particularly the oxygen in it, contained a mysterious “life force” of some kind which was needed to generate organisms spontaneously. They would undoubtedly argue that microorganisms failed to appear in Pasteur’s sealed flasks because he had killed this “life force” when he heated the air to sterilize it.

To refute this argument, Pasteur developed a clever new type of experiment. The idea for it came from Balard, his old master, who often dropped in at the little laboratory to watch the progress of his former pupil.

A flask was half-filled with yeast water, then its neck was heated until the glass melted and could be pulled out to form a long, curved tube. This was called a “swan-neck” flask because of its shape. (See drawing on next page.)

The flask was then boiled to kill the microorganisms in the liquid and, at the same time, the air was driven out by steam. As the liquid cooled, air could enter again through the open end of the swan-neck. But microorganisms floating in this air were trapped; they dropped and settled onto the long, curved neck before they could reach the liquid in the flask.

In arranging this experiment, Pasteur was fulfilling the conditions which—according to the advocates of spontaneous generation—ought to be very favorable for it. Plenty of ordinary, unheated air could reach the yeast water; thus, there was nothing to keep out the “life force”—whatever it might be. Yet, as long as Pasteur kept the swan-neck flask perfectly quiet, no microorganisms appeared. Weeks and even months could pass—and still the yeast water stayed clear.

Flasks used in Pasteur's spontaneous generation research. At the top is the type he carried to trap air in Paris and in the Alps. At bottom is a swan-neck flask. The tubing is open at the end.

But when he tilted the flask for an instant, some of the microorganisms deposited on the swan-neck would fall into the liquid. Soon little threads would appear in the yeast water and it would grow cloudy—evidence that the microorganisms were growing and multiplying.

After three months of experimentation, Pasteur felt he was ready to fire his opening gun in the battle, with a report to the Academy of Sciences on his new experiments. He rejected the theory that spontaneous generation was brought about by some strange life force in the air, whether it be “gases, fluids, electricity, magnetism, ozone, or anything else known or unknown.” Nothing in the air could produce living organisms in his sterile liquids, Pasteur stated, except for the germs that were floating in it.

“Ridiculous!” retorted Pouchet. “Do you mean to say that there are germs enough in the air to reproduce themselves in all such liquids, everywhere? Why, if this were true, the germs would form a mist as dense as iron!”

Pasteur stood his ground and laid plans to attack from another angle. Pouchet, he knew, claimed that ordinary air would always bring about spontaneous generation when conditions were favorable. In other words, the naturalist believed that microorganisms would always appear in a sterile nutrient bouillon if it were exposed to unheated air. Pasteur thought this very unlikely because he suspected that microorganisms were not evenly distributed in the air. For instance, they would probably be found in far greater numbers in the dusty street of a city than on a mountaintop. He planned some new experiments to test this hypothesis.

A small flask was filled with sugared yeast water. The glass neck was heated and drawn out in a curve with a very narrow opening. (See top drawing on opposite page.) The liquid was boiled to kill all microorganisms and to drive out the air with steam. While the steam was still escaping, Pasteur quickly sealed the flask by melting the glass at the opening with a jet of flame from a blowpipe. In this way a vacuum was created in the flask.

He carried several of these sealed flasks to a spot where he wanted to collect a sample of air. With sterilized pincers, he broke off the glass tip of a flask. Air rushed into the vacuum. Then he quickly sealed the flask again with a flame, trapping the air.

Pasteur kept the sealed flasks in his incubator at a temperature of 25°C. to 30°C. (77°F. to 86°F.). If the liquid turned cloudy, it was evidence that living, microscopic bodies had been trapped along with the air.

He collected samples of air in many parts of Paris and got some interesting results. For instance, he opened and sealed eleven flasks in the courtyard of the Paris Observatory, where the wind was blowing and crowds of people were moving about. Then he carried ten more flasks down to a deep cellar of the observatory where people seldom came and the air was very still. He moved very slowly and cautiously, trying not to stir up the least bit of dust.

In all of the eleven flasks opened and resealed in the courtyard, the liquid soon became cloudy with microorganisms. Of the ten flasks opened in the cellar, the liquid in only one grew cloudy; the rest stayed clear. There seemed little doubt which place had the cleaner air.

When Pasteur went to Arbois for the summer vacation, he took along seventy-three sealed flasks. Some of these were opened and resealed in the country near his old home. Then the scientist resolved to trap the purest air he could possibly find. He would climb the Alps!

At the town of Chamonix he hired a guide for the climb up to the glacier called Mer de Glace. He loaded a case of thirty-three flasks on a mule and started off close behind the animal, steadying the case with his hand so his precious flasks would not be broken.

At the glacier Pasteur failed in his first attempt to trap air. The wind was strong and the glare of the ice dazzled him. He could not see the flame of his little alcohol lamp, so he could not be sure his flasks were resealed properly after they were opened. He went back to the inn and had a tinsmith fix the lamp to make the flame more visible. The next morning he climbed up to the glacier again.

With very great care Pasteur heated the neck of a flask in the flame of his lamp, to kill any germs that might have collected there. He raised the flask high above his head to keep it away from the dust of his clothes. Then he broke off the tip with his sterilized pincers, let the air rush in, and quickly resealed it.

Working in this way, Pasteur succeeded in trapping air in twenty flasks. The liquid in all but one stayed clear and free from microorganisms. The mountain air did, indeed, seem to be purer than the air in the dusty cities below.

In the meantime Pouchet, too, was collecting air above the sea, on Mount Etna and on the plains of Sicily. The naturalist reported results exactly opposite to those of Pasteur. “Everywhere the air is equally favorable to the spontaneous generation of life,” he insisted flatly. “With a cubic decimeter of air, taken wherever you like, I assert that you can always produce great numbers of microorganisms.”

By this time scientists in France and abroad were follow-ing the contest with keen interest. The Academy of Sciences offered a prize for the best attempt, “by carefully conducted experiments, to throw new light on the question of so-called spontaneous generation.”

“What will be the outcome of this battle of the giants?” demanded a writer in one scientific journal. Another journalist warned, “I am afraid the experiments you quote, Monsieur Pasteur, will turn against you. . . . The world into which you wish to take us is really too fantastic.”

Early in November, Pasteur dramatically placed his seventy-three flasks on the desk of the academy, with a report on the nonspontaneous source of the microorganisms to be found in them. In addition, he gave a clear hint that he already suspected some of these odd, microscopic bodies of being very dangerous. “What would be most desirable, he suggested, “would be to push these studies far enough to prepare the way for serious research on the origin of various diseases.” He did not name any of the diseases he wanted to see conquered. But anyone who knew him could be sure that one target he had in mind was typhoid fever, the relentless killer of his daughter, Jeanne.

With his report to the academy, Pasteur dropped the subject of spontaneous generation for the time being. He felt that he had made his point and he was anxious to get back to his fermentation research.

In his laboratory he now had a long row of sealed flasks in which the liquid would stay fresh and clear indefinitely. Some of the flasks contained sugared yeast water. Others held boiled milk or urine, liquids which ordinarily would spoil quickly. But these samples would not spoil because he had kept away from them the microorganisms that brought about putrefaction.

Pasteur stored the flasks away carefully. They would make good ammunition for the next round in his battle with Pouchet.

8

Life Without Air

WHILE STUDYING the fermentation which produces butyric acid (the acid formed as butter becomes rancid), Pasteur made a surprising discovery.

Under the microscope, he saw some very tiny, short rods, rounded at the ends. They were spinning about and shaking themselves, sometimes bending almost double. So lively were they that he assumed they were microscopic animals or “animalcules” as they were sometimes called.

“They must be feeding on the microorganisms that produce the butyric acid ferment,” the scientist mused. “I’ll have to get rid of them.” Finally he realized the “animalcules” were the ferment itself.

One day he put a drop of liquid undergoing butyric acid fermentation on a glass slide and placed over it a thin glass cover slip. When he observed the flattened drop of liquid under the microscope, he noticed a curious fact. At the center of the drop, the tiny rods were as lively as ever. Around the edges, they had stopped moving.

Now this behavior was very strange! It was exactly opposite to what Pasteur had learned to expect from animalcules when he had studied them in a flattened drop under a glass cover slip. Ordinarily they tried to get close to the edge of the drop where they would find more air.

Could it be that these microorganisms did not need air— that it was even harmful to them ?

He tried forcing a current of air through a flask in which a butyric acid fermentation was taking place. Soon he observed that the fermentation had been stopped.

Next, he passed some carbon dioxide gas through a similar butyric acid fermentation. Ordinarily a dose of this gas would be deadly to animalcules, but the microorganisms causing the butyric acid ferment were not bothered by it in the least. The fermentation kept on as actively as before.

To Pasteur, this was very astonishing. Although scientists disagreed about many things, they were generally in agreement that plants and animals needed “free” oxygen to live— oxygen in the form found in the air. Now he had discovered microorganisms that not only did not need air—it killed them!

In February, 1861, he reported his discovery to the Academy of Sciences. He stated with pride, “This is, I believe, the first known example of animal ferments and also of animals living without free oxygen.”

Later Pasteur realized he had been mistaken in thinking that the lively little rods were animals. They were, in fact, a species of bacterium—and bacteria are considered plants. Such an error was easy to make in the early days of the science of microbiology. And the distinction between microscopic plants and animals was especially confusing for Pasteur who had been trained as a chemist, not as a naturalist.

He was probably also mistaken in thinking he had been the first to observe microorganisms that could live without air—although in 1861, no one questioned his claim. Modern scholars who have studied the writings of Antony van Leeuwenhoek, the Dutch discoverer of microorganisms, believe that he sighted these same little “animals” as long ago as 1680. However, Pasteur was the first scientist to recognize the importance of the discovery of microscopic organisms living without air— as well as the first to study them and find a name for them. Consulting the professor of Greek at his school, he decided to call them anaerobic microorganisms. Those that needed air to live he called aerobic.

Pasteur’s discovery brought yet another puzzle. Whenever he had carried out a butyric acid fermentation in his laboratory, he had made no attempt to shield it from the air. Why didn’t the microorganisms die under these conditions?

He worked out a new theory to answer this question, although he did not succeed in proving it conclusively for some years. “Aerobic microorganisms must manage to slip into the liquid undergoing butyric acid fermentation,” he thought. “They use up the free oxygen in the solution and form a film on its surface. This film protects the anaerobic microorganisms underneath from the air, so they can bring about fermentation into butyric acid.”

Pasteur carried his speculations still further. He had noticed that when butter became rancid—or any other butyric acid fermentation took place—a bad-smelling gas was produced. This led him to wonder if anaerobic microorganisms might be at work in the process called putrefaction, when meat, eggs, and other protein foods spoil with an unpleasant smell.

As he followed this line of thought, he came to realize the important role that microorganisms play in clearing the earth of dead animals, fruit, plants, trees, and other living things. Pasteur first outlined his theory in a letter to the Minister of Public Education.

When the sweet juice of a plant or a fruit is left to itself, Pasteur explained, air brings to it a little microscopic plant— yeast—which transforms the sugar into alcohol and carbon dioxide. Then other kinds of microorganisms oxidize the alcohol to acetic acid. Still others complete the process of oxidation, changing the acetic acid to water and carbon dioxide. And so at last practically all of the elements that make up the sugar—carbon, oxygen, and hydrogen—are returned to the atmosphere.

He went on to point out that when an animal dies in the forest, its flesh, organs, and other parts are invaded by microorganisms in much the same way. Some kinds break down the tissues into chemical compounds, then these compounds are in turn broken down into simpler compounds, including water, ammonia, carbon dioxide, and other food for plants. The plants in turn are eaten by man and other animals— thus completing the “cycle of life,” as scientists call it.

“If the remains of dead plants and animals were not destroyed,” Pasteur declared, “the surface of the earth would soon become cluttered with organic matter and life would become impossible because the cycle of transformation . . . could no longer be closed.”

He had a purpose in writing to the minister in such detail. Since Pasteur was still dependent on the government for money, he found it wise to report not only on his current research but on his plans for the future as well.

“You can foresee from this, Monsieur the Minister,” he now emphasized, “how useful it is to cover the field of these studies which offer so many analogies to various animal and plant diseases. They are certainly a first step on the very desirable path of serious research on putrid and contagious diseases.”

Meanwhile Pasteur was proving the importance of his laboratory with a research project of immediate, practical value. The vinegar makers of Orleans were having serious trouble with their product and they called on him for help.

Vinegar was produced from alcohol and alcohol-containing liquids such as wine or beer. The alcohol was fermented into acetic acid, giving vinegar its sour taste. But the vinegar manufacturers had no accurate knowledge of what agent or agents brought about fermentation; they even disagreed on whether these agents were chemicals or living organisms. Consequently, vinegar-making was a rather uncertain, hit-or-miss procedure.

At Orleans, Pasteur studied the fermentation process with a scientist’s thoroughness and precision. He gave particular attention to the thin layer of film that covered the vinegar in the vats. In this film he isolated the fermenting agent— a tiny microscopic plant called mycoderma aceti. He showed the manufacturers how to encourage and control the growth of this microorganism so that their vinegar would develop more successfully.

New honors were steadily coming to Louis Pasteur. In December, 1862, the Academy of Sciences awarded him its prize for his experiments refuting the doctrine of spontaneous generation. In the same month he was elected a member of that famous academy. His election was especially satisfying for him because twice before he had been a candidate and had been defeated.

Membership in the academy gave Pasteur new standing among scientists. The following March the members were invited by Emperor Napoleon III to a reception at the palace of the Tuileries. Since the Revolution of 1848, the government had changed again and the country was now an empire.

When Pasteur was presented to the Emperor, Napoleon III greeted him cordially and discussed with interest the scientist’s research projects. Pasteur seized the chance to tell the Emperor of his great ambition to fight disease.

That year Pasteur spent his summer vacation at Arbois, studying wines and why they sometimes spoiled. During the same summer Pouchet was still fighting the battle of spontaneous generation with the help of two ardent supporters, Nicholas Joly and Charles Musset.

Since Pasteur had collected air high in the mountains, Pouchet and his aides resolved to do it, too. Furthermore they would outdo Pasteur, who had reached a spot only sixty-five hundred feet above sea level. They determined to climb up to a glacier in the Pyrenees Mountains, between France and Spain. They would trap samples of air four thousand feet higher!

Pouchet, Joly, and Musset spent a cold, uncomfortable night camping on a mountainside so they could climb the next day to the highest possible spot. Joly was almost killed when he slipped into a crevasse. A guide grabbed him just in time.

The three scientists tried conscientiously to keep their flasks sterile and to trap only the pure mountain air. But in spite of their care, they soon found that all their flasks were swarming with microorganisms.

Triumphantly Pouchet announced to the Academy of Sciences, “The production of a new being without parents is for us a reality!” In reply, Pasteur proposed that a commission of the academy be formed to pass on his experiments and those of Pouchet, Joly, and Musset. Rather nervously, Pouchet asked that the test be postponed; he wanted to avoid the danger of freezing weather for his microorganisms, he explained.

Pasteur expressed polite surprise at the request for a delay. “With a stove,” he suggested, “it would have been easy to raise the temperature to the degree desired by these gentlemen.” But he was agreeable to a postponement because he was extremely busy just then. He had been invited to lecture on spontaneous generation at one of the “scientific evenings” being held at the Sorbonne.

The fashionable and literary folk of Paris, as well as the scientists, were now watching the “battle of the giants.” On the night of the lecture the great hall of the Sorbonne was packed. People filled the aisles and steps, squeezing into every square inch of space. Among the celebrities were the elder Alexander Dumas, George Sand, and Princess Ma-thilde, a famous hostess and the cousin of Napoleon III.

With the aid of slides, Pasteur gave an illustrated talk on the fascinating organisms which he had trapped in the atmosphere. The lecture was a great success and became the talk of Paris for days.

In June of 1864, the commission demanded by Pasteur finally met at the Museum of Natural History. He came armed with dozens of flasks, including three he had opened and sealed again in the pure air of the Alps, four years before. The liquid was still clear and free from any sign of microorganisms.

While the commission watched, one of these flasks was broken open to let in the dust-laden air of the room. Within three days the judges could see small masses of microorganisms growing in the liquid.

Pasteur carried out an impressive series of demonstrations but, at the last minute, Pouchet, Joly, and Musset hedged and backed down. They argued that they would need many months and many more experiments to prove their point. Accordingly the judges decided in Pasteur’s favor.

Oddly enough, Pouchet might have won the battle, at least for a time. If he had dared to repeat his experiments before the judges, he could have produced microorganisms that seemed to be spontaneously generated. Pasteur did not then have the knowledge he needed to explain Pouchet’s results.

He did eventually solve the mystery of Pouchet’s flasks. However, that did not happen until more than twelve years later when still another scientist challenged him in the long battle over spontaneous generation.

9

A New Word for the World-Pasteurization

TWO MONTHS after Pasteur gave his demonstration before the academy commission, he went home to Arbois. Throughout his busy life, he loved to spend a part of each summer in the little mountain village where he grew up. He always planned plenty of work for these “vacations.” This year he hoped to find a remedy for the diseases of wine.

Arbois was located in one of the great wine-producing regions of France and many of Pasteur’s old neighbors had vineyards, including his boyhood friend, Jules Vercel. Ordinarily the wines made from these grapes were in demand in foreign countries as well as in France. Sometimes, however, for some unknown reason the wine turned cloudy and flat-tasting. Naturally no one wanted to buy this spoiled wine and the grape growers lost money.

Wine makers in all the grape-growing regions of France were having much the same trouble. In some cases their wines became cloudy and flat, like those of Arbois. In other regions the wines had a different disease—they became very bitter. In still other areas the wines became oily or acid. Various theories were advanced for this alarming situation. One school of wine makers believed that oxygen was harmful, so they tried to shield their wines from the air. Other producers disputed this view, claiming that oxygen was needed to age wine properly.

Pasteur had gotten his first clue to the trouble during the summer of 1858, soon after he announced his discovery of the lactic acid ferment. When he went to Arbois on vacation, he had taken along a microscope. In some cloudy, flat-tasting wine he had spotted little oblong bodies which looked very much like those he had discovered in his lactic acid fermentations. But he did not then follow the clue of the little oblongs—at that time his interest was not in wine diseases but in developing his theory of living organisms as the cause of fermentation.

During the next few years, as he studied the fermentation of wine along with other types of fermentation, the problem of the diseases of wine cropped up again and again. Pasteur could not forget it; the matter was serious not only for his Arbois neighbors but for the whole French wine industry. He began to formulate some theories on why wine spoiled. And when Napoleon III heard of Pasteur’s interest in the problem, the Emperor urged him to find a solution.

Pasteur had begun a systematic study of wine diseases the previous summer, while Pouchet, Joly, and Musset were scrambling around in the Pyrenees. Now, in September of 1864, he made ready for his second season of research in the wine country. He took several assistants to Arbois with him.

He set up a laboratory in a deserted old cafe near his father's house. Pasteur and his men hauled water from the town fountain for their experiments and washed dishes in the river which ran just behind the cafe. Since there was no gas supply, they got their heat from a charcoal brazier, keep¬ing the flame going with a pair of bellows. And whenever they needed a new piece of equipment, they had it made by the village tinsmith, blacksmith, or carpenter.

Jules Verccl and the other grape growers were glad enough to furnish Pasteur with samples of their wines for study. At first they were rather amused by all this scientific equipment and note-taking, but Pasteur soon made them take his research seriously. ^

When he was given samples of the spoiled wine, he would put a drop of each one under the microscope. "This wine is bitter," he would announce positively. "And that one is acid."

The wine makers were amazed. "Why, how can you tell?" they demanded. "You haven't even tasted it!"

The explanation lay in the scientist's microscopic studies. He had learned that the deposit in every flat-tasting wine contained not only yeast but also the tiny oblong globules of his lactic acid fermentations. Every sample of acid wine contained quite a different microorganism—the mycoderma aceti. From Pasteur's vinegar research he knew that this organism changed the alcohol in wine into acetic acid. Bitter wine, too, contained its characteristic microorganism and so did the wine that had turned oily.

Pasteur’s discovery of these unwelcome visitors explained why some grape growers had found it a good idea to shield their wine from the air. While they thought they were protecting the wine from oxygen, in reality they were keeping harmful microorganisms from dropping into their vats. Oxygen, itself, was not harmful, as Pasteur proved by means of chemical studies. On the contrary it was needed for the proper aging of wine.

Microorganisms of healthy and diseased wine as seen under the microscope:

1. in a normal fermentation; 2. acid wine; 5. oily wine; 4. bitter wine.

But discovering the cause of wine diseases was only half the job. How could keep wine from getting sick?

This proved to be a more difficult problem than keeping beet juice or vinegar from spoiling. Pasteur had shown Bigo and the other manufacturers how to make good alcohol by sowing healthy yeast cells into their juice. He had taught the vinegar makers to improve their product by sowing into it plenty of healthy mycoderma aceti.

But wine makers did not have to sow yeast into grape juice. The wild yeast cells just seemed to appear mysteriously on the grapes at the time of the harvest. Pasteur believed they were clinging to the grapevines or floating in the air, like the other almost invisible microorganisms he had trapped in his spontaneous generation experiments.

Consequently he had to work out an entirely new method to keep wine from spoiling. He would have to find a way to kill the harmful microorganisms in it—without harming the taste of the wine.

First he tried using antiseptics but they were not satisfactory. Then he hit on the idea of using heat. By experimentation he learned to hold the temperature of the wine at between 50° and 6o° C. (122^0 F. to 140° F.) for a few minutes. A heat lower than this would not get rid of the microorganisms. A higher temperature would spoil the taste.

Pasteur designed special equipment so wine makers could heat their product safely and efficiently. The following April he obtained a patent for his method but he freely gave the use of it to all wine makers. His only purpose in patenting was to prevent anyone from monopolizing and exploiting his discovery. He had followed the same practice in patenting his process for making vinegar.

Of course the idea that heat helped to preserve wine and food was not new; men had stumbled on it a long time before. Pasteur, however, was the first man to show clearly why heat protected food and to put its use on a sound scientific basis.

It took a number of years and many tests before the wine makers were convinced that heating could protect their wines without changing the taste. Eventually they accepted the process and later it was also adopted to kill disease-carrying germs in milk, butter, cheese, and other foods. Pasteurization is now a familiar word in many languages.

Heating wine to hill disease microorganisms, by the process that became known as pasteurization. This drawing was published in the second edition of Pasteur's book on wine diseases, to show how one wine maker built his pasteurizing apparatus. The man in the foreground operates a pump which forces air into the top of the cask at the left, causing the wine to flow through the tubing into the heater, placed just outside the archway. Here the wine passes through a series of tubes in which it is heated with boiling water and then cooled with a refrigerant. Finally it flows into the cask at the right. Ordinarily, wine makers used a much simpler apparatus; many heated the wine after it had been bottled.

10

Pasteur Tackles the Silkworm Disease

AS LOUIS PASTEUR entered his laboratory one spring day in 1865, he looked perplexed and rather worried.

“Do you know what Monsieur Dumas has just asked me to do?” he demanded of his assistant, Emile Duclaux. “He wants me to go south and study the disease of silkworms!” Dumas, his former chemistry professor, was now a senator representing one of the regions where silkworms were raised. He told Pasteur they were dying in a disastrous epidemic. Unless it was stopped, thousands of growers would be ruined and an important French industry wiped out.

“I did not even know that silkworms had a disease,” Pasteur protested to Dumas. He had no background for such a study; he had never even touched a silkworm. But he was fond of his old teacher and hated to refuse the request of a man who had given him much help and encouragement.

Moreover Pasteurs interest as a scientist was aroused. He had studied the diseases of wine and vinegar—could these have any connection with the disease of silkworms?

In spite of the big risk of failure, he accepted the appointment as head of a research mission for the government. He asked Dumas to keep the assignment secret for a few days, until he could look over the situation and decide whether he might be able to accomplish something.

Early in June he went to Alais in the mountains of southern France, near the Mediterranean Sea. The town was a center of the silkworm industry.

One of his first acts was to visit Jean Henri Fabre, the great French naturalist and writer on insects, who lived nearby.

“I have never seen a cocoon,” Pasteur confessed. “Could you get me one?”

“Nothing could be simpler,” answered Fabre. He stepped out to see a neighboring grower and came back with a hand-full of the pale gold, oval balls.

Pasteur picked up a cocoon and examined it curiously. He turned it over and over, then put it close to his ear and shook it.

“It rattles!” he said. “There is something inside.”

Fabre smiled. “Of course. It is the chrysalis.”

“The chrysalis! What is that?”

Fabre opened the cocoon and showed Pasteur the little dried-up body inside. He explained that the silkworm, or caterpillar, spins the cocoon around itself for protection. Safe inside its cocoon home, the caterpillar changes into a chrysalis or pupa which in turn changes into a moth. The moth breaks out of the cocoon, mates, and lays eggs—six hundred to eight hundred at one time. They look rather like very tiny vegetable seeds.

The following spring a caterpillar hatches from each egg. It feeds greedily on mulberry leaves and grows so fast it soon splits its skin (molts). Underneath the old skin is a larger skin which stretches as the silkworm grows. Within about five weeks after hatching it molts four times.

The full-grown caterpillar is about three inches long. It climbs on a twig and makes its cocoon by spinning a silk thread from its body, much as the spider spins the thread for its web. The life cycle of the silkworm—from the hatching of the egg until the moth lays a new brood of eggs—takes about two months.

Fabre explained to Pasteur that when a grower wants to harvest the silk, he does not let the moth burst out of the cocoon. That would break the thread and it could not be unwound. Instead, he puts the cocoon in a steam bath to kill the chrysalis, after which the silky ball is dried. It was this dead chrysalis that rattled when Pasteur shook it.

Unfortunately, silkworms that were weakened by disease could not spin good cocoons. Sometimes they died in the midst of their spinning, leaving their work half finished. Or they might die before they even began to spin.

Pasteur and his assistants set up headquarters in a nursery near town. He knew he would have to work fast to make any progress that year. Within a month the cocoons and eggs for hatching would be harvested and the season would end.

He ranged up and down the countryside questioning growers and examining their broods. Many of the men were rude and unfriendly. They had already tried so many desperate measures without success. At great expense they had imported supposedly healthy eggs from Japan—only to get more diseased silkworms. They had also experimented with dozens of recommended remedies, including sulfur, coal tar, powdered mustard, ashes, rum, and wine. Nothing had worked. How could this prying chemist help them to save their nurseries?

Before leaving Paris, Pasteur had read a long report on the silkworm disease. It was called pébrine, from pebre, a word for pepper. The sick worms were usually spotted with little black specks that looked like grains of pepper. Also, scientists who studied sickly worms under the microscope had sometimes seen small, oval, shiny cells which they called corpuscles. Some observers believed these were related to pébrine. Others thought there was no connection.

Pasteur decided to center his first research on the corpuscles. He examined hundreds of silkworms, giving special attention to two broods of worms in the nursery where he had his headquarters. He watched these broods closely as they developed.

The worms of one brood spun very fine, healthy cocoons. Yet when he examined the chrysalises and moths of that brood, he found them swarming with corpuscles.

The worms of the second brood were sickly and slow to develop and they spun poor cocoons. When he opened them, he found very few or no corpuscles. Day by day he kept opening and examining a few of the brood as they changed into chrysalises and then into moths. The older the chrysalises grew, the more corpuscles they had. By the time the moths developed, not a single one was free of corpuscles.

Conditions in the other nurseries around Alais were just as confusing and apparently contradictory. Nevertheless Pasteur decided that the corpuscles did, indeed, seem to be an indication of the silkworm disease.

Just nineteen days after arriving in Alais, he appeared before a meeting of the growers to give his first recommendations for fighting pébrine. Certainly he did not like to work as fast as this. As a scientist he would have preferred to keep quiet about his conclusions until he had tested them. Usually he did not discuss them even with his assistants until he was almost ready for publication in a scientific journal.

But the silkworm study was a special case. It was an official project and an emergency. Pasteur knew if he kept silent, the growers would have no help for another whole year.

He warned, “Do not assume that eggs are healthy because the moth that laid them came from a fine-looking cocoon. That moth might be full of corpuscles—then its descendants would be poor, sickly spinners of cocoons.”

Some investigators, he reminded his audience, had already advised searching the eggs and worms for corpuscles, so that broods showing these suspicious cells could be destroyed. But this was not enough to insure a good harvest; the corpuscles might not show up until the chrysalis or moth stage.

To make sure of a healthy brood, Pasteur continued, the best plan was to isolate each pair of moths until they had mated and laid eggs. Then both the male and female should be opened and studied under the microscope. If either moth in a pair showed signs of corpuscles, their eggs should be destroyed. But if both moths were free of corpuscles, their eggs could be considered pure and should be saved for hatching the following spring.

As the scientist finished speaking, he was not surprised to see doubt and disappointment on the faces of the growers. His egg selection method could not help them much now— they would have to keep on buying expensive eggs from Japan. So widespread was the disease that it was almost impossible to find healthy moths. Pasteur himself had examined hundreds of moths before he could find just two pairs that were free from corpuscles.

At any rate, not until the next silkworm season would he or his audience know whether or not his advice had been sound.

This first year of silkworm research was a tragic time for Pasteur. He had barely begun his work in June when his father died suddenly in Arbois. Then, on returning to Paris from Alais in early July, he found his two-year-old daughter Camille very ill with a liver disease. Pasteur watched her through two heartbreaking months until September when she died.

The end of November brought him an experience of a very different kind. Napoleon III and Empress Eugenie invited the scientist to spend a week at their splendid palace at Compiegne. Madame Pasteur stayed home but Louis wrote her very long letters describing the activities.

On the first evening before dinner, Pasteur assembled in a handsome drawing room with his fellow guests—ambassadors, writers, and other famous people. Generals glittered with medals and gold braid; ladies in beautiful gowns sparkled with jewels. Pasteur wore the formal court costume with knee breeches and silk stockings.

The gentlemen formed one long line and the ladies another. While the Empress greeted the ladies, the Emperor passed down the line of gentlemen. When Pasteur was presented, Napoleon III said affably, “Oh, yes, I’ve been wanting for a long time to congratulate you on your fine studies. You are continuing them, I hope?” Pasteur assured him that he was.

After dinner the two lines formed again and the Empress greeted the gentlemen. She, too, gave Pasteur a warm welcome. During the evening Napoleon drew him over to the fireplace and questioned him about ferments, wine diseases, and right-handed and left-handed crystals. It was decided that Pasteur should give a demonstration of some of the microorganisms he had discovered. Even the Empress commanded, “Monsieur Pasteur, you must not show these things just to the Emperor. I want to see them, too.”

That night before going to bed, Pasteur wrote to Marie for his microscope and case of instruments. He also gave her exact directions for finding certain labeled bottles of diseased wine in his cellar.

The next day he rode out into the forest in an open carriage drawn by six horses, to see a stag hunt. In the evening came the climax to the hunt, when the carcass of the stag was thrown to the hounds in the great courtyard blazing in the light of torches. Pasteur watched with the rest of the guests from the windows of the palace. On another evening he went to a play performed by some of France’s leading actors.

As a special mark of favor, the Empress invited him to the first of a series of five o’clock teas she was giving for groups of the guests. He did not receive the invitation in time to go. He was down in the royal cellars, hunting for some bottles of diseased wine for his demonstration.

On Sunday afternoon, at four o’clock, he had his private meeting with Their Majesties. For an hour he showed them some of the queer living things in what Pasteur liked to call his world of the “infinitely small.”

By this time the guests of the Empress were gathering for tea. “Monsieur Pasteur, they should learn something of your studies!” she announced. She picked up the microscope and gaily led the way to the tea party.

Pasteur then gave the guests a short, simple talk on science and some of his investigations. No speaker could have wished for more attentive or respectful listeners.

11

The Riddle of the Corpuscles

IN FEBRUARY, 1866, Louis Pasteur returned to Alais for his second year of silkworm research. With his assistants he rented a comfortable house at the foot of a mountain, about a mile from town. Around it were mulberry bushes and olive trees. A hothouse was fixed up as a laboratory and silkworm nursery.

When spring vacation came, Madame Pasteur started for Alais with her two daughters while Jean Baptiste stayed in school at Paris. On the way twelve-year-old Cecile fell ill of typhoid fever, and she died within a few weeks.

“Our beloved children die one after another,” the grief-stricken father wrote. Jeanne—Camille—and now Cecile— how helpless he was to protect them! It had been six years since Jeanne, too, had died of typhoid fever and the doctors were still as ignorant as ever of its cause. Of the Pasteurs’ four daughters, only Marie Louise was left.

At Alais, Madame Pasteur became her husband’s secretary. Every evening he dictated answers to letters and notes for articles. Even Marie Louise, eight years old, found ways to help. She went up on the mountain with her father to pick mulberry leaves. She also learned to examine silkworms with the microscope and to spot the odd corpuscles that seemed somehow to be related to pébrine.

During the growing seasons of 1866 and 1867, Pasteur set up a series of experiments to study the silkworm under all sorts of conditions. He and his assistants watched the development of worms hatched from the eggs of both diseased moths and healthy ones. They studied the effect of differences in temperature.

Some silkworms were fed on wet, bruised leaves, others on leaves smeared with the remains of sickly worms. Certain broods were given damaged leaves during their second molt and others not until the third or fourth. Pasteur kept a faithful record of the exact conditions under which each brood was raised.

He also visited growers in the neighborhood. He was eager to see what luck they had when they took his advice to hatch only the eggs of moths free from corpuscles. In general the results were encouraging. Some angry growers, however, reported that their broods were sick even though they had followed his instructions.

Pasteur was able to clear up much of the trouble by working out a more accurate technique for detecting corpuscles in the moths. In time, his recommendations for selecting eggs proved to be a good, practical method of getting rid of pébrine in the nurseries.

But there were still some puzzling failures, and for almost two years he worked in vain to find the reason for them. His experiments seemed to indicate that pébrine might be a contagious disease—yet he could not pinpoint any agent that spread the contagion.

What threw him off the track was the riddle of the corpuscles. Actually, these tiny oval cells were the transmitting agent of contagion that he was searching for. But he did not realize this fact at first because he fell into one of the traps always waiting for scientists who do research. He confused a cause with a result.

It is easy to see now why Pasteur made this mistake. In his first year of research, when he had made a special study of the two broods in his own nursery, he had observed that worms could become sick and show no sign of corpuscles until many days later. In some of his later experiments, healthy worms had eaten leaves smeared with bits of tissue from corpuscular worms; they had died quickly without showing any trace of the mysterious oval cells.

Accordingly Pasteur concluded that the corpuscles could not be the cause of pébrine. He believed instead that they were simply a result of it—probably some change in the tissues that took place as the disease ran its course.

Another factor misled him, too. “If corpuscles were living organisms,” he reasoned, “they would be able to reproduce themselves.” So far as he could discover, the corpuscles did not have a mode of reproduction as did the yeast cells and other ferments he had often watched under his microscope. He did not know that the oval cells were protozoa, a type of microorganism with which he was not familiar. Their method of reproduction was different from that of yeast cells—and much harder to detect.

“But why do our broods get sick?” the growers demanded.

It was partly a matter of heredity, Pasteur explained. Healthy moths, showing no corpuscles, were more apt to produce healthy eggs and worms. Environment was a factor, too. A sudden change of temperature, crowding, bad feeding conditions—all these could cause trouble.

By the spring of 1867, it became clear that a piece of the puzzle was still missing. One of Pasteur’s own broods died unexpectedly after the first molt. The dead worms were black and soft and rotted quickly. A microscopic examination showed not a trace of corpuscles.

As the discouraging reports from other growers piled up, Pasteur grew gloomier and gloomier. His staff noticed that he was upset but, as usual, he kept his thoughts to himself. Finally one day he burst out, almost in tears, “Nothing has been accomplished. There are two diseases!”

He cheered up when he realized that at last he might have the key to the puzzle. Searching through the silkworm literature, he found that some investigators had mentioned a disease called flacherie that exactly fitted the description of his soft, rotting worms. Now that Pasteur’s method of egg selection had largely eliminated pébrine, flacherie stood out more clearly as a second disease.

The scientist went back over the record of his earlier experiments. This was a time when his very detailed, careful note-taking paid off; it cleared up many puzzling points.

For example, he checked his notes on those two broods he had studied during his first few days at Alais. He could be fairly sure now that the second brood—the worms that had become sick without having corpuscles—must have been suffering at first from flacherie. Later they had also caught pébrine, and then they had shown the corpuscles.

Flacherie was evidently contagious, too. Now that Pasteur had recognized it as a distinct disease, he was able to study it and learn how to control it.

Still, he had been right in concluding that feeding conditions, temperature, and other circumstances of environment were factors in the diseases, particularly in the case of flacherie. The silkworm, he learned, was a much more complicated living thing than the microorganisms in beet juice or wine. In studying it, Louis Pasteur was moving another step toward understanding disease in human beings.

12

Pasteur, the Fighter

IN THE SUMMER of 1868, Madame Pasteur’s father wrote her that he was worried about her safety. He had heard that Pasteur had been chased from Alais by angry silkworm growers who were throwing stones at him!

Although the report was exaggerated, it was true that the scientist was being attacked from several sides. Some of his critics were growers whose harvest had failed even though they followed his advice. Others were the merchants who imported silkworm eggs from Japan and sold them at a stiff price. They knew their profits would vanish if Pasteur taught each grower to pick healthy eggs from his own nursery.

And finally he was criticized by many biologists and naturalists who were outraged that a mere chemist would dare to tackle a biological problem such as the diseases of silkworms.

His friends tried to persuade him to ignore these attacks but Pasteur insisted on fighting back. Every time a critical article about his methods and findings appeared in a newspaper or magazine, he quickly fired off a reply. He answered every letter he received—whether friendly or unfriendly—dictating his answers to his faithful secretary, Madame Pasteur. He also gave many lectures before scientific groups defending his ideas.

This battling had begun when Louis Pasteur was a young chemist defying the great Liebig, and it continued during all of his scientific career. It took a great deal of time and energy but it did have some good results. Because he was so determined to meet every objection, he often carried out extra experiments which shed new light on the problem he was investigating. Because he could and did shout as loudly as his noisiest opponent, he won attention and respect for his views more quickly than a quieter and more retiring scientist might have done.

Fortunately, Pasteur always had many loyal supporters as well as enemies. While some groups were attacking him, others would be showering him with honors. About the time his father-in-law heard that he was being chased out of Alais, the celebrated University of Bonn in Germany awarded him the honorary degree of Doctor of Medicine.

A silkworm moth and its eggs. Pasteur used this sketch to explain his method of selecting eggs free from pébrine. After the eggs are laid on the square of linen, the cloth is folded and pinned together to make a little bag in which both moth and eggs are kept until the moth can be examined microscopically. If it contains corpuscles, its eggs are destroyed. For extra assurance of healthy broods, Pasteur recommended a similar examination of the male in each pair (shown pinned within the cloth at the bottom).

Together with his silkworm disputes, he was fighting the battle of the laboratory. He badly needed more room for his research. He sent a very persuasive letter to Napoleon III, pointing out that he must have a place where he could keep experimental animals and study infectious diseases without endangering anyone. The Emperor gave orders that Pasteur should have his laboratory. But soon all plans were stopped —the government, it seemed, could find no money for it!

Pasteur wrote a fiery article of protest. Other countries were building rich and large laboratories, he said, among them Germany, Russia, England, and America. Meanwhile French scientists had to work in attics and damp, dark cellars, and use their own money for equipment. As Pasteur had intended, the article was read by Napoleon III who summoned him to a conference. After a long, anxious wait, he received in July the good news that his laboratory would be built after all.

In spite of these battles Pasteur made good progress during the summer against the second silkworm disease—flacherie. He taught the growers to spot sick worms by their sluggish movements. He had also learned that worms suffering from flacherie had certain kinds of bacteria in their digestive tract, so he showed growers how to detect these bacteria with a microscopic examination. “Pick a few moths from each brood for study,” he said. “Extract a small piece of the digestive tract of a moth with the point of a scalpel. Mix this with a little water and examine it under the microscope.” If the moths did not contain any of the suspicious bacteria, Pasteur explained, the strain from which they came could be considered suitable for breeding.

He worked long hours in his own laboratory and nursery and traveled through southern France under the hot summer sun, interviewing growers and inspecting their nurseries. When he returned to Paris in the fall, he was busier than ever—teaching at the Sorbonne, carrying out new experiments, answering his silkworm critics, writing a book about the diseases of silkworms, and overseeing the building of his laboratory. He drove himself so hard that he became very pale and tired-looking, but he refused to slow down.

One day in October he noticed a strange tingling sensation in his left side. He paid no attention to it because he was anxious to read a paper at the Academy of Sciences that afternoon. It was a report from an Italian scientist who had studied Pasteur’s work on silkworms and strongly approved it.

When Pasteur went to bed that night, he had the tingling feeling again; soon afterward he found he could not speak or move. Making a great effort, he managed to call Madame Pasteur who sent for the doctor. By morning his whole left side was paralyzed. He had had a cerebral hemorrhage.

During the next few days Pasteur’s life was in great danger. “I am sorry to die,” he murmured once. “I wanted to do much more for my country.”

Madame Pasteur and his closest friends took turns watching by his bedside. Scientists and officials of the government and the imperial court came to inquire about him. They sat in a small study, the room farthest from the bedroom, so their voices would not disturb him. Each morning the Emperor and Empress sent a footman for a report which the doctor wrote out and dispatched to the palace in a sealed envelope.

But the man who had fought so strongly for his ideas and his laboratory was ready to fight just as hard for his life. In a week the crisis had passed and Pasteur began to improve. His first act was to dictate a memo on his silkworm research, a new method he had just thought of for detecting eggs that were likely to hatch into worms with flacherie.

One thing made him restless and uneasy, however. The dining room of his apartment overlooked the gardens of the Ecole Normale, where his precious new laboratory was being built. He strained his ears for sounds of building activity but everything was quiet—much too quiet.

“How are they getting on?” he asked Madame Pasteur over and over. She would look out the window and give him a vague report but he soon found out the truth. The day after his attack of paralysis, someone in the government had ordered all work to be stopped. Why waste money finishing a laboratory for Pasteur, since he was going to die ?

The next time General Fave, the Emperor’s aide-de-camp, came to call, the patient complained indignantly. If everyone was so sure of his death, it would be more honest and straightforward to tell him about it!

The general carried the message to Napoleon. Soon Pasteur was cheered to hear the noise of construction work again.

13

War—and the Search for Jean Baptiste

BY THE END of the year Pasteur had regained enough strength to take a few steps without help. He was impatient to get back to the silkworm country. An agricultural society there, in the town of St. Hippolyte du Fort, was planning tests on forced silkworms according to a method he had recommended. In forcing, a few eggs from each brood were heated to make them hatch earlier than normally. The young worms were examined microscopically so that a grower could detect and destroy unhealthy broods before the rest of the eggs were allowed to hatch.

Overruling the objections of his wife and friends, Pasteur insisted on attending the forcing tests. On January 18, 1869, just three months after his attack of paralysis, he was bundled up and carried to the train departing for the south. At St. Hippolyte du Fort he supervised the testing program and continued his slow recovery, grimly practicing walking by leaning on Marie’s arm. Then he went to Alais for the regular growing season.

Pasteur was now confident that he had completely solved the problem of how to select eggs that would produce good silkworms. With the help of his microscope, he could predict the success or failure of a brood. He used this skill to impress his critics, just as he had impressed wine makers by telling them whether a wine was bitter, acid, or flat without having tasted it.

In March the Lyons Silks Commission asked him for some guaranteed healthy eggs to be hatched in their experimental nursery. Knowing that some members of the commission were still very skeptical of his findings, Pasteur decided to give them a little demonstration. In addition to the healthy eggs the commission asked for, he sent them four other lots of eggs. And he boldly made these predictions:

Lot No. 1, he said, would produce healthy silkworms.

Lot No. 2 would die exclusively from pébrine.

Lot No. 3 would die exclusively from flacherie.

Lot No. 4 would die partly from pébrine and partly from flacherie.

Several months later the commission admitted that the sample lots had behaved exactly as predicted.

In the fall, Pasteur had a chance to make an even more spectacular demonstration of his methods. The Prince Imperial, Napoleon’s son, owned an estate called Villa Vicentina, near the city of Trieste on the Adriatic Sea. Once a flourishing silkworm farm, the estate had been ruined by pébrine and flacherie. Marshal Vaillant, minister of the Emperor’s household, suggested that Louis Pasteur be invited to try to make the farm productive again.

“It is an opportunity to vanquish your opposition,” said the marshal. Moreover, he pointed out, a winter in the warm, sunny countryside of southern Europe would help the scientist to regain his health.

Pasteur agreed to go, and he and his family traveled southeastward to Trieste, making the trip by short stages because he was still very weak. They spent a happy, peaceful winter at Villa Vicentina, in a big white house set among lawns and trees. Pasteur’s neighbors made him feel welcome and sought the honor of meeting him for, by this time, silkworm growers in Italy and Austria were watching his research with respectful attention. Besides learning how to prevent silkworm diseases, Pasteur himself had become expert at raising productive broods. Under his direction, the Prince’s run-down estate became a model silkworm farm.

While Pasteur waited for the harvest, he finished his manuscript on silkworm diseases—which by this time had grown lengthy enough to fill two volumes. The book was ready for publication in April. Of course, he did not miss the chance to preach on his favorite theme—the importance of microorganisms. In his introduction he wrote, “The role of these infinitely small beings appears to me to be infinitely great, whether as the cause of different diseases, particularly contagious ones, or by contributing to decomposition and to the return to the atmosphere of everything that has lived.”

The harvest of cocoons that season at Villa Vicentina was a great success. After all expenses were paid, the Prince’s farm showed a profit of twenty-two thousand francs—the first it had earned in ten years.

Early in July, 1870, the Pasteurs started home to Paris. On the way they stopped at Strasbourg, the town where Pasteur had held his first university post and where he had met and married Marie.

Strasbourg was the capital of the province of Alsace, on the border with Germany, and it was here that Pasteur first heard very alarming news—France and Germany were on the brink of war. Absorbed in his silkworm studies, the scientist had not known of the growing tension between the two countries. And when he left Strasbourg after his two-day visit, he had no intimation that he would never see the city again, or that all Alsace would soon be seized and annexed by a victorious Germany.

The Pasteurs had been back in Paris less than a week when Napoleon III declared war, provoked into taking that step by the wily and ambitious Prussian chancellor, Otto von Bismarck. Bismarck’s powerful army invaded Alsace, inflicting defeat after defeat on the French Emperor and his unprepared troops. On September 2, Napoleon III and one hundred thousand French soldiers were captured in a great battle at Sedan. The way was open for the Germans to drive straight to Paris.

Pasteur was appalled by the disaster that was overwhelming his country so swiftly. He determined to help defend Paris by enlisting in the National Guard. His friends discouraged this idea by convincing him that he would be rejected. Age was not the reason—he was only forty-seven. But his left arm was still paralyzed from his recent illness and his hand was stiff and useless. His left leg, too, was very stiff and dragged when he walked.

As the citizens of Paris hastily prepared their city for a siege, the intensely patriotic Pasteur suffered in knowing there was absolutely no way he could help. He could not even continue his research because the school building was being turned into a hospital. All of the students had enlisted, as well as his eighteen-year-old son, Jean Baptiste.

Pasteur’s old friend, Bertin, who was now an administrator at the Ecole Normale, urged him to leave Paris. At first Pasteur refused, but he gave in when the anxious Bertin argued, “You have no right to stay! You would only be one more useless mouth to feed during the siege.”

Before the Germans could surround the city and cut off escape, Pasteur left for Arbois with his wife and Marie Louise. He had kept the old tannery building as a vacation home since the death of his father, sharing it with his sister and brother-in-law, who had taken over Jean Joseph’s business.

For the first few weeks in Arbois, the little hill town seemed a long way off from the fighting. Now and then Pasteur would hear the sound of a trumpet, the signal that the town crier had a new bulletin to announce. He would gather with the other citizens at the bridge over the river and listen to the news which, week by week, became more serious.

When Pasteur heard that the Germans had bombarded Paris, hitting the Ecole Normale and the Museum of Natural History, he protested in the only way he knew how. He indignantly returned the honorary degree he had accepted less than three years before from the University of Bonn.

He tried to keep his mind occupied by studying the process of tanning, in which fermentation brings about the softening and curing of hides to make leather. He also watched his sister’s bread-making, studying how the fermentation of yeast caused dough to rise and speculating on ways to make bread cheaper and more nourishing.

But he could not forget the war. The Prussians were coming closer and closer to Arbois. News came that the army in which Jean Baptiste was fighting had been defeated and was retreating in great confusion toward Pontarlier, across the mountains from Arbois and close to the Swiss border.

Pasteur waited in vain for news of his son until at last he could stand the suspense no longer. He resolved to go in search of Jean Baptiste. Certainly, the finding of one young soldier in a disorganized army of thousands of men would seem an impossible task—but Pasteur was used to tackling the impossible.

He rented a dilapidated old carriage, the last one to be found in the village. On January 24 he set off with Madame Pasteur and Marie Louise over the snow-covered mountain roads.

The family had a slow, cold, exhausting journey. The old carriage creaked and groaned; now and then it stuck in snowdrifts and had to be pulled out. At night the Pasteurs slept in little inns, and by the third night they had reached Chaffois, a few miles from Pontarlier. They were now in the midst of the retreating army. Everywhere were groups of ragged, exhausted soldiers, begging for food and a little straw to sleep on. Other soldiers stumbled along the road on frostbitten feet.

At Pontarlier the Pasteurs went from group to group seeking news of Jean Baptiste’s battalion. “All I can tell you,” said one soldier to Madame Pasteur, “is that out of the twelve hundred men in that battalion, only three hundred are left.”

At last they found a soldier who knew of Jean Baptiste. “Corporal Pasteur? Yes, he is alive; I slept by him last night at Chaffois. He stayed behind; he is sick. Perhaps you will meet him on the road to Chaffois.”

The Pasteurs started back the way they had come. Just outside Pontarlier they saw an old cart coming toward them. A thin soldier wrapped in his overcoat was in it, gripping the sides of the cart to keep his balance. It was Jean Baptiste!

The reunited family followed the route of the retreating army into Switzerland, where the soldiers were being interned by the neutral Swiss. After a few days of good nursing by Madame Pasteur, Jean Baptiste rejoined his battalion. Pasteur, his wife, and Marie Louise returned to France, going southward to Lyons, the home of Madame Pasteur’s sister and brother-in-law.

Where was the wandering scientist to go next? He did not want to return to Arbois, for the town had fallen and was now a Prussian supply depot—besides, he was chafing to get back to a laboratory. Paris was out of the question; since the city’s surrender it had been in the grip of a bloody civil war. Pasteur thought briefly of going to Italy, where he had been offered professorships at either Pisa or Milan— whichever place he preferred. But he refused the tempting Italian offers. He would feel like a deserter, he explained, if he left his country while it was at war.

Then an invitation came to him from Emile Duclaux, one of his former assistants, who was now a professor of chemistry at Clermont-Ferrand in the silkworm country. Duclaux urged Pasteur to bring his wife and daughter and stay with the Duclaux family until Paris quieted down again.

The middle of April, the Pasteurs traveled to Clermont-Ferrand. There Pasteur started on some silkworm research but he soon became intrigued by an interesting fermentation problem. Near the town was a brewery and the scientist, as curious as ever, began investigating the manufacture of beer.

He discovered that brewers were having much the same kind of trouble that had disturbed the manufacturers of beetroot alcohol, vinegar, and wine. Beer often became thick, sour, acid, or slimy—and no one knew why. Pasteur lost no time in getting samples of the spoiled beer under the microscope. Just as he had anticipated, he found swarms of trouble-making microorganisms mixed in with the yeast that brought about fermentation. The thick beer contained one type; the acid beer had another; the slimy beer, still another.

He plunged energetically into the problem of getting rid of the troublemakers. He had a patriotic reason for taking up this study. His old patron Napoleon III had been deposed and a newly formed republican government was struggling to recover from the war. With the signing of the peace treaty in May, 1871, the new French republic had promised to pay to Germany within three years an indemnity of five billion francs—about one billion dollars. If Pasteur could teach French brewers to make superior beer, he thought hopefully, he would be helping another industry of his country and would thus indirectly help in paying off France’s staggering debt.

Pasteur’s research on beer continued for five years following the war and during that time he did succeed in improving French beer and eliminating its diseases. He designed special apparatus for pasteurizing it as he had done for the wine makers. In short, his research helped the brewing industry—in other countries as well as in France—just as his earlier studies had aided the industries producing beetroot alcohol, vinegar, wine, and silkworms.

Some years later, the English biologist Thomas Henry Huxley was to say in a lecture, “The discoveries of Pasteur have paid back to France the five billion francs demanded by Germany after the war of 1870.”

However, during Pasteur’s beer studies he kept getting sidetracked—from the problem of brewing better beer into a deep investigation of the chemical and biological aspects of fermentation. He himself did not like the taste of beer— he was much more interested in it as a fermentation problem than as a beverage. As a result of his research, he was finally able to support with solid evidence some of the theories on fermentation that he had advanced many years before. These important new findings he presented in a book, Studies on Beer, which he dedicated in a grateful and loving preface to the memory of his father—the tanner of Arbois who had backed his son so loyally during Louis Pasteur’s long struggle for an education.

After four months in Clermont-Ferrand Pasteur returned to Paris, which had once again been restored to order after civil war. Early in September he went to England to study that country’s brewing methods. English brewers, too, were being plagued by diseased beer and Pasteur showed them how a microscope could help to clear up the trouble.

But the high spot of his trip was a meeting with John Tyndall, an English physicist who firmly supported what had come to be known as the “germ theory of disease.” From Tyndall Pasteur heard a report on the achievements of Joseph Lister, then a professor of surgery in Scotland. Lister had been much impressed by Pasteur’s studies of the invisible little organisms that were floating in the air, and that had the ability to bring about fermentation and putrefaction. The English surgeon realized that similar microorganisms might carry infection into a wound during an operation. On this theory he had developed his method of preventing infection by killing the germs with antiseptics.

Pasteur felt pleased and encouraged in hearing about Lister’s success. A few scientists, at least, were beginning to understand that these “infinitely small” plants and animals could be dangerous enemies of man.

14

Can Germs Cause Disease?

IN MARCH OF 1873, Louis Pasteur was elected an associate member of the Academy of Medicine. At his first meeting he found himself in the midst of a hot debate on the germ theory of disease.

A certain Dr. Onimus had presented a paper on “The Influence of Inferior Organisms, Developed During Putrefaction, on the Putrid Poisoning of Animals.” Onimus had to admit that very tiny organisms were present in cases of infection—“putrid infections” as he called them. Anyone with a microscope could see that. But, he claimed, these organisms were not harmful or poisonous. They were simply the result of putrefaction and decay—not the cause.

“No, putrid infections are caused by microorganisms,” insisted Dr. Casimir Joseph Davaine, a physician who had made some experiments supporting the germ theory. Then Dr. Bouillaud, the presiding officer, called on the newest member for his views.

Pasteur began hesitantly. Before him were the most important and influential physicians and surgeons of Paris. Some of them looked rather amused and patronizing. Some were downright unfriendly. These were the members who had tried to keep this “mere chemist” out of the academy; he had won election by a margin of only one vote.

“I had not intended to take the floor today,” Pasteur explained. “I will say only a few words in reply to Monsieur Bouillaud’s kind invitation.” He added that he supported the views of Davaine. But he was careful to point out that this was only his opinion since he had not carried out experiments on the subject.

Then he went on to describe a case in which he had proved, through exhaustive experimentation, that a certain disease was due to a certain kind of microorganism. Some of the doctors exchanged smiles. Pasteur was telling them about a disease of beer!

He summed up slowly, gesturing with his good right arm. “The correlation is certain, indisputable, between the disease and the presence of the organisms.” He was so emphatic that the stenographer recording the debate underlined these final words. But, aside from the stenographer’s reaction, the new member’s statement caused no excitement.

Pasteur made it a regular habit to attend the Tuesday meetings of the academy. He would sit quietly at desk number 5 which had been assigned to him, listening to the debates but saying little, like a new boy in a strange school. It was indeed a strange world for a chemist. According to a saying of that time—a century ago—physicians and surgeons were the “princes of science” and they considered themselves somewhat above such men as chemists, naturalists, and physiologists. Most of the medical “princes” believed that physiology could teach them little or nothing about treating the sick—and certainly, they had very little use for chemistry.

One of the favorite targets of their scorn was the germ theory of disease. Except for Davaine and a scattering of other progressive medical men, the members scoffed at the idea that these odd little organisms could cause disease and infect wounds.

“How ridiculous,” they said, “to think that tiny plants and animals—so small you need a microscope to see them— could be powerful enough to kill a man or a horse!”

They further declared, “Disease or the putrefaction of wounds is something that just appears spontaneously, perhaps when the body is weakened by poor food or living conditions. In some people, disease may take the form which we call typhoid fever. In others, it becomes tuberculosis or possibly diphtheria.

“But,” they stated firmly, “there is no such thing as a specific disease, due to a specific cause.”

One doctor had even warned the academy, “The doctrine of specificity would condemn us to finding a specific remedy for each of scores of diseases. Why—it would halt the progress of medicine!”

While the majority of the members jeered at the germ theory, Pasteur was getting a practical education in medical matters outside the academy. He made friends with several doctors and went with them to visit their patients in the Paris hospitals. Often he was horrified by the things he saw.

Surgeons in blood-covered aprons went from one operation to the next with only a quick rinsing of hands and instruments—and sometimes with no washing at all. Bandages smeared with pus were thrown carelessly about. Even patients who came through an operation successfully were very apt to die anyway, for infection entered the wounds, spreading through their bodies while the doctors were helpless to stop it.

Hospitals were considered deathtraps. Their air was thought to be poisonous and thousands of patients died from a mysterious illness called “hospital miasma.”

An exception among the surgeons was Dr. Alphonse Guérin. Like Joseph Lister, he had developed a new type of dressing for wounds based on Pasteur’s research. Guérin would wash them with a solution of alcohol or carbolic acid, then cover them with cotton to protect them from germs floating in the air.

Although Pasteur was delighted with the success of Guérin’s dressings, he was able to suggest an improvement. “Heat the cotton first to a very high temperature,” he advised. “In this way you can make sure all germs on the cotton are killed.”

Most of the surgeons, however, showed little interest in adopting the bandages of Guérin, whom they thought somewhat eccentric. They continued their same germ-spreading practices until finally Pasteur could keep silent no longer. Before he had been a member of the Academy of Medicine a year, he started giving advice to the doctors not only at their Tuesday meetings but also at the Monday meetings of the Academy of Sciences. In the beginning, he tried to be tactful.

“If I had the honor of being a surgeon,” he said on one occasion, “I would never introduce into the human body an instrument without having passed it through boiling water or, better still, through a flame.” So completely new to most of his listeners was the idea of sterilization that they did not understand what he meant. Some surgeons thought Pasteur was telling them to operate with very hot instruments! He had to explain that the only purpose of heat was to kill the germs that stuck in the tiny grooves of an instrument even after careful washing.

Pasteur now found that he had more freedom to carry on research than ever before. Since he could no longer teach because of his health, the government had awarded him a pension of twelve thousand francs a year—the salary of a professor at the Sorbonne—in recognition of the millions of francs he had saved French industries by his studies. His friends were pleased to think he would have a chance to rest—but Pasteur had other ideas. He made it clear that he would “retire” only on condition that he could keep his precious laboratory.

He had given it a new name—the Laboratory of Physiological Chemistry—for his experiments were coming steadily closer to problems of disease in animals and human beings. In one project, he studied a type of fermentation that sometimes occurred in the urine of sick people and made a report of his findings to both academies.

A small group of young doctors and medical students were beginning to listen to''Pasteur with growing interest and respect. He was cheered, too, by a friendly letter from Lister thanking him “for having, by your brilliant researches, demonstrated to me the truth of the germ theory of putrefaction.”

But most of the French doctors were irritated at having this upstart chemist invade their field. They criticized his findings and conclusions and Pasteur did not hesitate to answer back. He was no longer shy about speaking up when he found flaws in their statements and experiments—and he no longer always bothered to be tactful. He was particularly impatient with the members’ habit of speaking of “orators” and “speeches.” “Let us leave these words to political meetings,” he recommended. “They seem to me incompatible with simplicity and scientific precision.”

One subject that came up again and again was the old controversy over spontaneous generation. Physicians who denied that germs caused disease had to explain somehow why these microorganisms were present in the blood and tissues of sick people. Usually they fell back on the explanation that they appeared spontaneously, as a result of the disease. In confusing cause and result, they were making the same mistake Pasteur himself had made during his silkworm studies, before he solved the riddle of the corpuscles.

“I’ve searched for spontaneous generation for twenty years, without finding it!” he cried during one debate. Pasteur never said spontaneous generation was impossible; he merely stated that, as a scientist, he could find no evidence of it.

His cleverest opponent in this latest round of the old battle was a young English physician. Dr. Henry Charlton Bastian had copied some of the experiments Pasteur and Pouchet had carried on a dozen years before and he claimed that he had succeeded in spontaneously generating bacteria. The Englishman was so eager to prove his claims that he came to Paris to meet Pasteur before a commission of the Academy of Sciences.

Pasteur grumbled at having to waste time on more experiments in the old battle. Again he won the decision but, even so, his contest with Bastian was worthwhile, for he discovered that his methods of sterilization were not yet good enough to kill all germs. Moreover his new studies solved an old mystery—he found out at last why Pouchet had seemed to produce microorganisms “spontaneously” in spite of that scientist’s best efforts to keep his flasks sterile.

Instead of making a nutrient bouillon of yeast water, as Pasteur had done, Pouchet had used a liquid in which hay had been steeped. The bacteria in this hay were so tough they could survive the boiling he gave them. But they needed oxygen to develop, so they stayed dormant until he let air into the flasks.

As a result of these new findings, Pasteur worked out techniques for sterilizing at higher temperatures, either in an oven or with steam that had been superheated by putting it under pressure. At first most of his steam sterilizing was done in three great basins with covers. Every now and then the laboratory was rocked by an explosion from the high pressure. The cover of a basin would blow off with a roar and boiling liquid would shoot up to the ceiling.

One of Pasteur’s assistants, Charles Edouard Chamberland, developed an explosion-proof apparatus called the autoclave. It is still used by hospitals for safe, thorough sterilization of instruments, dressings, and other equipment where disease-carrying germs might be hidden.

15

The Conquest of Anthrax Begins

AT THE AGE of fifty-four, Louis Pasteur felt he was  ready to start on the project he had been working toward so long—research on contagious diseases.

The first step was to get money for his new studies. In February, 1877, he appealed to the Minister of Public Education, as he had done so many times before. Pasteur began his letter:

“Although I am a stranger to the fields of medicine and the veterinary art, the sum total of my work of these past twenty years has brought me close to the difficult problem of the causes of contagious and infectious diseases.” He went on to explain that it was his intention to study septic poisoning and anthrax. He would need extra money to buy animals for experiments and to arrange for a place to keep them. Also needed would be books and translations of scientific reports—as well as the salary for a young medical doctor whom Pasteur would need to assist him on this research program.

“Accordingly, Monsieur the Minister,” he summed up, “I have the honor to propose that your Excellency grant an increase of sixty-five hundred francs in the year’s budget for my laboratory.”

So impatient was Pasteur to begin his study of anthrax that he did not even wait for the minister’s reply. Two days later he wrote to a veterinary surgeon named Boutet, who lived near Chartres, asking for some “anthrax blood”— blood of a sheep which had died of that disease.

Anthrax was a strange and devastating ailment that killed thousands of sheep and other farm animals every year. The fields where the animals died were said to be “cursed.” When farmers let flocks graze in them, the new sheep often died, too—even when the “cursed” fields had not been used for grazing for many years.

Pasteur had long wanted to study anthrax and he had watched with interest the research carried out by other scientists. As early as 1850 it had been investigated by Casimir Joseph Davaine, the physician who had defended the germ theory on the day Pasteur attended his first meeting at the Academy of Medicine.

Davaine had examined under the microscope the blood and tissues of an animal dead from anthrax and had noticed great numbers of tiny, straight rods. In 1861 he read Pasteur’s report on the “animalcules” that caused butyric acid fermentation, and it occurred to him that the little rods might be the same ferment or, at any rate, might cause anthrax in somewhat the same way. He inoculated rabbits with anthrax blood. The rabbits died and the same tiny rods could be found in their blood.

Davaine had shown these queer rodlike microorganisms to Pasteur who could easily see that they were quite different from his butyric acid ferment. Pasteur thought they were probably not closely related to it. But at that time, in 1863, he had no background for studying whether this microorganism might cause a disease like anthrax.

Two other French scientists, Leplat and Jaillard, disputed Davaine’s findings before the Academy of Sciences. They had killed a rabbit by inoculating it with anthrax blood that was full of the microscopic rods. Yet when they examined the dead rabbit, they found no trace of these microorganisms. Therefore, they claimed, the tiny rods must simply be one result of anthrax—not its cause.

Davaine countered this by contending that the inoculated rabbit had died not of anthrax but of a different disease— septicemia, or septic blood poisoning. Pasteur agreed. But neither he nor Davaine had convincing experiments to offer in support of their belief that anthrax was caused by the rod bacteria.

In 1876 Robert Koch, a German physician, succeeded for the first time in growing the bacilli outside the body. (All types of bacteria having the shape of rods are known as bacilli from the Latin word for “little sticks.”) For his nutrient bouillon, Koch had used a drop of the watery liquid from the eye of an ox. After the bacilli had multiplied, he transferred a few of them to a second drop of liquid and let them grow. He made a similar transfer eight times. Then he injected a little of the eighth drop into a mouse. In twenty-four hours the mouse was dead and in its spleen were the same familiar bacilli—the same type of little rods.

Koch also discovered why sheep sometimes caught anthrax by grazing in a “cursed field.” When he let the bacilli grow in a culture, they developed into a mass of twisted threads on which sprouted little balls called spores. The spores had a very tough cover that protected them from dryness, heat, cold, and other unfavorable conditions. They could stay alive for years without food or water. Then, when conditions were favorable again (for instance, when a sheep grazing in a field swallowed them), they could change into the deadly bacilli.

But Robert Koch’s precise, careful experiments could not convince some scientists who remembered the contradictory experiments of Leplat and Jaillard. They insisted, “It is not the rod organism that kills sheep but some other substance in the blood and tissues—perhaps an invisible substance.”

Koch had obtained bacilli from an animal dead of anthrax and transferred these and their descendants into a fresh drop of liquid eight times. Thus, there was a very faint possibility that a bit of some other substance from the diseased animal might have been transferred from drop to drop along with the bacilli.

Pasteur decided on an experiment that would close this possible loophole. He filled a flask with fifty cubic centimeters (nearly two ounces) of sterile urine. Into this nutrient bouillon he sowed a single drop of anthrax blood that Boutet had sent him from Chartres—blood that was full of the little rods. After several hours they had multiplied until the flask was swarming with them.

Pasteur took a single drop of this culture and sowed it into a second flask containing fifty cubic centimeters of sterile urine. When the second flask was full of the rod bacteria, he transferred a single drop of this second culture to a third flask.

He repeated this process a hundred times! Then he took some of the culture from the one hundredth flask and inoculated rabbits and guinea pigs with it. They all died, showing the signs of the dreaded anthrax. And the characteristic rods could be found in their blood.

“The rod organisms must be the cause of anthrax,” Pasteur concluded. Nothing else from the original drop of diseased blood was left. It had been diluted a hundred times, as though it had been lost in all the water of all the oceans of the world. The red and white corpuscles had been lost; the liquid part of the blood had been thinned until all its molecules were lost in the bouillon. The only things remaining were the tiny rods, descendants of the bacilli that had originally been in the blood of the diseased sheep.

But how could the findings of Leplat and Jaillard be explained? Other scientists, too, were claiming they could give an animal anthrax by inoculating it with blood that did not contain the bacilli.

Pasteur’s studies had suggested an answer to this question. In June he went to Chartres to see Boutet. The veterinarian had ready for his inspection three animals that had died of anthrax. They had been chosen according to Pasteur’s instructions.

Pasteur first examined a sheep that had been dead about sixteen hours. Its blood was full of the rod bacteria.

Next he examined a horse that had died the day before. In addition to some of the rods, its blood contained a different kind of bacterium—a long, thin, flexible one so transparent it was almost invisible. As Pasteur described it, “It slips between the corpuscles of the blood the way a snake slips through high grasses.” He had first spotted this odd microorganism the year before and had named it the septic vibrio.

Finally, he examined the third animal Boutet had saved for him, a cow that had died more than two days before. Its blood was swarming with septic vibrios but contained only a few of the rod bacteria.

Pasteur’s next step was to inject some blood from the sheep into a guinea pig. It soon died and its blood was found to be full of the familiar rods. Then he inoculated two other guinea pigs with blood from the horse and the cow. They, too, died very quickly, but their blood contained no rods.

The scientist explained his theory in this way: “The septic vibrio is found in the intestinal canal of all men and animals, even healthy ones. When death comes, from anthrax or from any other cause, the septic vibrio slips into the bloodstream. It begins to multiply swiftly in the first step of the process of putrefaction. In contrast, the anthrax bacteria stop multiplying after death and gradually disappear.

“The horse and cow,” Pasteur continued, “had been dead long enough for septic vibrios to invade their blood. When I injected this blood into the second and third guinea pigs, I gave the vibrios a chance to get into the animals’ bloodstream. These guinea pigs died of septicemia—blood poisoning—not of anthrax.”

Pasteur reported his first findings and conclusions on anthrax to the academies. As usual his reports were opposed, particularly in the Academy of Medicine. His bitterest critic was G. Colin, a professor at the veterinary school at Alfort.

Colin had tangled several times with the quick-witted Pasteur at academy meetings and had made a poor showing. Now he saw his chance. He boasted that he had made five hundred experiments on anthrax and that Pasteur was completely wrong in saying that it was caused by the rod bacteria.

Furthermore, Colin contradicted Pasteur even on minor points. For example Pasteur happened to mention in his report that chickens did not catch anthrax.

“Nonsense!” said Colin. “Nothing is easier than to give anthrax to hens.”

Pasteur felt he could not let such a flat contradiction pass. Since he was trying hard to win the respect of medical men, he always avoided making statements in the academy that he could not back up with proof.

“Well then,” he asked Colin politely, “will you be good enough to bring me a hen suffering from anthrax?”

Colin agreed without giving the matter much thought. He had not yet learned the danger of contradicting a Pasteur who felt sure of his facts. Before long he would find out.

16

The Three Hens

IN MARCH, 1878, Pasteur won powerful new support for the germ theory of disease. Dr. Charles Emmanuel Sedillot, a prominent surgeon, lectured before the Academy of Sciences on “The Influence of Monsieur Pasteur s Work on Medicine and Surgery.” It was in this speech that Dr. Sedillot first suggested the word microbe for microscopic organisms. Pasteur promptly adopted this “new and happy term.”

The same month he was being praised in the Academy of Sciences, he was attacked in the Academy of Medicine. Colin presented experiments which he claimed proved that Pasteur was wrong—that the rod bacteria were not the cause of anthrax.

When Pasteur rose to reply, he concluded with the story of Colin’s promise to give anthrax to a hen. He had often asked for the sick hen since then, he said, but Colin had failed to produce it. Then, “one day, about two months ago,” Pasteur added, “Monsieur Colin confessed to me that he was mistaken; it was impossible to give anthrax to a hen.” Pasteur explained blandly, “I have told this story to show that our colleague’s contradictions of our findings on anthrax —like his promise to give anthrax to a hen—are not to be taken too seriously.”

Then Colin’s turn came to speak. It was true, he admitted, that he had unsuccessfully inoculated two hens with anthrax bacteria. But he tried to dismiss the whole matter as merely a joke. “The experiment might have succeeded after all,” he said lightly, “but a hungry dog got into the cage. He ate the two hens.”

The following Tuesday as the members arrived for their meeting, they were amazed to see Pasteur getting out of a carriage with a cage in his hands. It contained a white hen, a speckled hen, and a black one. The white hen was dead.

When Pasteur was given the floor in the day’s debate, he put the cage on the speaker’s desk. At noon on the previous Sunday, he announced, he had inoculated the white hen with five drops of yeast water containing anthrax germs. It had died on Monday afternoon at five o’clock, just twenty-nine hours later. “We verified this morning that its body was filled with anthrax bacteria,” he stated.

There could be no doubt Pasteur had succeeded where

Colin had failed—he had given anthrax to a hen! How had he accomplished this? Chickens, the scientist explained to the members, normally have a body temperature several degrees higher than that of animals susceptible to anthrax. It had occurred to Pasteur that this higher body temperature might help to protect the chickens against anthrax germs.

He continued, sounding rather as though he were giving a demonstration before one of his science classes, “Let us take this white hen as a subject to test our preconceived idea. In other words let us try, immediately after the inoculation of the hen, to lower by some degrees the temperature of its body. Nothing is easier. We use a water bath, in which we plunge the lower one-third of its body. The hen dies the next day; its blood, spleen, lungs, and liver are filled with anthrax bacteria. In all of our experiments, we have not had a single exception.”

As usual Pasteur tried to anticipate objections. Some people, he pointed out, would say it was the cold bath that had killed the white hen—not the anthrax germs. Therefore he had given the speckled hen just as cold a bath, during exactly the same length of time. But he had not injected it with germs and it had stayed lively and healthy.

He also called attention to the black hen. It had been inoculated with ten drops of the yeast water filled with anthrax microbes—twice as strong a dose as the white hen had received. But its body temperature had not been lowered with a bath. “You can see how healthy it is,” he said with satisfaction.

A few weeks later Pasteur reported on a further experiment. He had inoculated a hen with anthrax bacteria and put it in a cold bath until it was very sick with all the signs of the disease. Then he took it out of the water, dried it and wrapped it snugly in cotton wool. He kept it warm until its body temperature returned to normal. The hen had recovered and was soon as lively as ever.

Louis Pasteur’s experiments with the hens were not simply stunts to show up Colin. He was always very curious about the role the natural defenses of the body can play in fighting off disease germs. He wanted to do much more research on this and similar physiological problems, but his life was not half long enough to study all the scientific puzzles that interested him. Today, of course, physiologists know that chilling the body can readily upset its defense system.

During the same period Pasteur was having his skirmish with Colin, he was working on the final draft of one of his most famous papers. He presented it in April to both academies. It was titled “The Germ Theory and Its Applications to Medicine and Surgery.”

Pasteur no longer had to limit himself to discussing a microbe that caused a disease in beer. He had now thoroughly studied the anthrax microbe and the septic vibrio, as well as a third type which he called a “microbe of pus.” He knew each germ’s habits, whether it was aerobic or anaerobic, and what living conditions it preferred. Further, he knew that each one would always produce its own specific disease. Never would the anthrax microbe cause septicemia or the septic vibrio cause anthrax. His findings explained why septic vibrios flourished in the blood of an animal after its death, while the anthrax germs gradually disappeared. Anthrax bacilli, being aerobic, need oxygen to grow and multiply, and when an animal stops breathing it ceases to get fresh supplies of oxygen in its blood stream. On the other hand, septic vibrios are anaerobic; they thrive best where there is no free oxygen.

In the meantime, Colin was still trying hard to give a hen anthrax—but without success because he failed to lower its body temperature sufficiently. Thoroughly baffled, he could not resist taking a sly dig at Pasteur. “I wish we could have seen the bacteria in that dead hen which Monsieur Pasteur showed us without taking it out of its cage,” he hinted at an academy meeting in July, “—that hen which he took away without letting us see the autopsy and microscopic examination.”

An angry Pasteur retorted to Colin’s insinuations. “I have always considered,” he told the members, “that my only right to a seat in this place is that given to me by your great kindness, since I have no medical or veterinary training. I therefore consider that I must be more scrupulously exact than anyone else in the presentations which I have the honor to make to you.” Whereupon he demanded that a commission be formed to examine his experiments.

At noon on the following Saturday, a commission of five solemn members met in the council room of the academy. Three dead hens and one live one were on the table. Pasteur explained the varying conditions under which each one had been inoculated.

At Pasteur’s insistence, Colin was delegated to be the examiner. He put a drop of blood from one of the dead hens under the microscope and studied it closely. Then he straightened up. “I am satisfied. It is not necessary to examine the others,” he conceded. Rather glumly he signed the commission’s report stating that there was no doubt of the presence of anthrax bacteria in the hen. Then he carried off one of the other dead chickens for a little private examination of his own.

Toward the end of 1878, a valuable recruit joined Pasteur’s laboratory staff. He was Emile Roux, one of the group of young medical men who admired the scientist and who had listened eagerly at the Academy of Medicine to his reports of his experiments.

Pasteur’s motto now was “Hunt the microbe!” He visited hospitals whenever he could get permission from doctors. With him were Roux and Chamberland, loaded with culture flasks. As he watched, the two young men would take samples of blood and tissue from sick people and from the bodies of those who had died of puzzling diseases.

Pasteur dreaded these hospital visits. An unusually sensitive man, he hated the sights and the smells. When his assistant cut open an abscess for a sample of pus, he winced as though he himself had been hurt. Nevertheless, he was determined to collect proof that would convince even the most stubborn doctor how dangerous disease-carrying germs could be. “I will make them see! They must see!” he kept repeating.

At this time he made a special target of an illness called “childbirth fever.” Healthy women who went to hospitals to bear their babies ran a serious risk of dying from this disease. Progressive doctors in several countries had come to realize it was an infection spread by bacteria; they tried to keep themselves and their hospitals as germ-free as possible with antiseptics and sterilization methods. But there were still many doctors who ridiculed these precautions.

One Tuesday at the Academy of Medicine a celebrated physician, Dr. Hervieux, was giving a lecture on the epidemics of childbirth fever that so often swept through maternity hospitals. He vaguely suggested some possible causes.

Pasteur kept quiet as long as he could—then he interrupted the speaker. “What causes the epidemic is nothing of the kind!” he protested. “Doctors and nurses carry a microbe from a sick woman to a healthy one.”

“If that is so,” replied Dr. Hervieux with a touch of sarcasm, “I am very much afraid the microbe will never be found—at least during my lifetime.”

Pasteur went to the blackboard and quickly drew a germ shaped like a long chain of beads. “There! That’s what it looks like!” he said.

It was the streptococcus. While rod-shaped bacteria are called “bacilli,” ball-shaped ones are generally known as “cocci” from a Greek word for “grain” or “seed.”

No one was safe from Pasteur’s needle when the scientist was on a microbe hunt. Soon after describing the streptococcus, he happened to notice that his friend, Emile Duclaux, had a boil on his neck. He asked Roux to take pus from it and several other boils Duclaux was suffering with. He sowed a bit of pus from each boil in sterile bouillon.

In each flask the same type of microbe began to grow and multiply. It was shaped like a cluster of tiny round dots. When Pasteur injected a culture of this microbe under the skin of guinea pigs and rabbits, small boils formed on them in turn—and each boil contained swarms of the same microbe.

Its family is well known today by the name Pasteur gave to it—staphylococcus, from a Greek word meaning “bunch of grapes.”

17

The Big Breakthrough

WHILE PASTEUR was tracking down new kinds of microbes, he did not neglect his study of anthrax. In fact he was successful in working out practical suggestions for farmers on how to keep the anthrax germs away from their flocks. But he was still not satisfied—he wanted to find a better way to fight the disease.

He spent many hours poring over the writings of Edward Jenner, the English physician who had introduced the practice of vaccination eighty years before. Jenner had protected people from smallpox by inoculating them with cowpox, a disease common to cattle. As the human body built up its defenses against the cowpox inoculation, it also seemed to defend itself from smallpox, which Jenner believed to be the same disease in a much more deadly form. Thus, vaccination was said to give the body immunity against smallpox.

“Perhaps,” Pasteur thought, “I can find out how to make animals immune to anthrax.”

It had already been observed by scientists that people and animals who recovered from certain diseases often seemed to be immune from getting those same diseases again. Pasteur himself had noticed that sometimes sheep could graze in a field infected with anthrax germs without catching the disease. He speculated that they might once have had anthrax in a form so mild the farmer did not recognize it. Somehow, this mild illness might have given them immunity.

Some investigators had tried to make animals immune by inoculating them with a mild form of a disease such as anthrax or pleuropneumonia, an illness of cattle. But “mild” doses, unfortunately, could not be depended on to stay mild. Often they flared up and killed the animal.

Accordingly Pasteur was faced with the problem: “How can I control the strength of an inoculation? How can I give an animal a mild case of anthrax without running the risk of killing it?”

His first efforts to develop a mild, safe form of anthrax were discouraging and fruitless. Then, through one of the strange accidents of science, he found his solution where he least expected it—in a program of research on chicken cholera!

Pasteur took up the study of this very contagious, deadly disease of chickens at the request of H. Toussaint, a young professor of physiology at the Toulouse Veterinary School. Toussaint and other scientists believed they had already found the cause of chicken cholera—a germ so tiny it looked like a speck under the microscope. The young physiologist had tried to grow it in a test tube but he was unsuccessful because he could not find the right nutrient bouillon for it. Puzzled, he turned to Pasteur for help.

Through experience Pasteur had learned that anthrax bacilli would flourish in either sterile urine or yeast water, so he first tried raising the new microbe in these nutrient bouillons. It would not grow in either one. Then he experimented with scores of other “recipes” for bouillons until at last he concocted one that proved successful. It was a broth made of chicken gristle, neutralized with potash and sterilized at a temperature of about 110°C. (230°F.).

In this broth Pasteur grew cultures of the tiny microbes. He inoculated healthy hens with the culture or put a few drops of it on crumbs which he fed to them. The hens died quickly, showing the symptoms of chicken cholera, and a microscopic examination revealed many of the same characteristic microbes in their tissues. These experiments certainly seemed to indicate that the microbes Pasteur had raised in his flask were as deadly to chickens as their parents had been. But before the scientist could make any detailed judgment of the deadliness—the virulence—of the little microbe, a much more thorough study of it would be necessary. To accomplish this, he mapped out a systematic program of experiments.

When summer came Pasteur went to Arbois, leaving his assistants, Roux and Chamberland, to continue the chicken cholera experiments. For once he had something more exciting than microbes to think about. His daughter was engaged to be married to a young writer, Rene Vallery-Radot. Pasteur was almost as pleased about the engagement as Marie Louise herself. He wrote the news to all his friends and began making plans for the wedding.

Meanwhile, in Paris, Roux and Chamberland were following their master’s program of experiments on the chicken cholera microbe. Every twenty-four hours they started a new culture by sowing a few microbes from the previous day’s culture in a flask of broth. They then inoculated chickens with the fresh culture, taking detailed notes on the changes in the condition of each chicken and the length of time before it died.

Then chance took a hand in the research and led the way to a startling discovery. Many versions have been printed about the famous “accident” that took place in Pasteur’s laboratory that summer of 1879—but here is the story according to Roux himself, who told it many years later to the scientist’s grandson, Pasteur Vallery-Radot.

One day Roux and Chamberland decided to take a holiday. They put their cultures of microbes away in a cupboard, locked up the laboratory, and were gone for several weeks. When they returned and started work again, they took one of the old cultures from the cupboard and inoculated a chicken with it. The chicken did not die; it did not even get sick. Evidently the culture had lost its strength during its stay in the cupboard.

The young men obtained some microbes from a diseased chicken on a nearby farm, prepared a fresh culture and injected it into several hens. All died on schedule—except one. With great surprise Roux and Chamberland realized that the lively survivor was the hen they had inoculated twice— with both the old culture and the fresh one.

They worried about this strange result; they knew their master disliked carelessness in experiments. Nevertheless, when Pasteur returned to the laboratory, they summoned up their courage and told him about the incident.

They started to apologize. “Be quiet!” Pasteur said sternly. He thought a moment, then burst out, “Well, that explains it—this hen was immunized when it was inoculated with the old culture!”

In this chance happening, Pasteur’s alert, “prepared mind” recognized a valuable new lead for his immunity studies and he enthusiastically went to work on it. “Probably the microbes kept their strength because we prepared a fresh culture of them every twenty-four hours,” he reasoned. “But why did the old culture become weakened while it was in the cupboard? And how can I duplicate it?”

His guess was that exposure to the oxygen of the air might have weakened the germs. Months of hard, routine experimentation followed, during which Pasteur tested this hypothesis. Fresh cultures of chicken cholera germs were placed in flasks which were then sealed shut with a flame, so that no additional air could reach them. Other freshly made cultures were put in flasks plugged only with cotton, so the air could filter in.

Germs in the sealed flasks, Pasteur learned, kept their deadliness for many months. In contrast, the germs exposed to the air soon lost their virulence.

The next step was to expose the cultures to air for varying lengths of time. In this way Pasteur found he could get a culture that was weakened to just the degree he wanted. He could then use it to immunize a chicken by giving the fowl a slight, harmless case of chicken cholera. And when he allowed these weakened germs to grow and multiply in a test tube, he found that their descendants were also weakened and gave only a mild case of the disease.

Pasteur described these weakened cultures as attenuated. And he adopted Jenner’s word vaccination for the process of inoculating with an attenuated culture to immunize against a disease. The attenuated culture itself he called a vaccine.

In February of 1880, he reported his vaccine discovery to the academies, giving his paper the rather sweeping title, “Virulent Diseases, Particularly the Disease Commonly called Chicken Cholera.” In his introduction Pasteur made it clear that his thoughts were going far beyond chicken cholera and other animal diseases. Among the greatest scourges of mankind, he declared, were “measles, scarlet fever, smallpox, yellow fever, and typhoid fever.” And in his conclusion he offered the hope that, “as a result of the facts that I have presented,” research could be undertaken on vaccines for “the virulent diseases that have so many times devastated and still devastate humanity.”

Pasteur was silent on one point, however. He said, “I ask the liberty, for the time being, not to reveal my method of attenuating a culture in order to keep my freedom of action for further studies.”

As he was to find out later, he could have saved himself a great deal of trouble by postponing the announcement of his discovery until he was ready to make a full report. But Pasteur’s laboratory was still being financed by the government and that put its chief under pressure to keep showing progress. Besides, he knew very well that his success in developing the first attenuated vaccine was a major breakthrough in medicine. It promised such exciting possibilities that he could not wait to tell the world about them.

18

Challenge to a Duel

TWO MONTHS after Pasteur announced his chicken cholera vaccine, he and his wife went to Arbois for a short visit. He had ordered some remodeling done on the old tannery building, to provide comfortable rooms for his daughter and son-in-law when they came for holidays. The plans included a nursery since the Pasteurs were looking forward to the birth of their first grandchild in the autumn.

He was also working on two more research papers. The longer of these dealt with further studies on the chicken cholera vaccine and its effects. Now that Pasteur had collected some evidence that germs caused disease and death, he was exploring the question of just how and why germs could kill an animal or human being. He had discovered some unexpected reactions in his inoculated chickens which, he believed, might throw new light on the nature of vaccine and disease.

Pasteur wrote and rewrote this paper before turning it over to Marie who prepared the final draft in her beautiful handwriting, as she had done for so many years. Then he made so many more corrections that she had to copy the whole thing over again. But she was game. “The academies will see how we spend the Easter holidays!” she wrote to Marie Louise.

At the end of April, 1880, Pasteur presented his new paper on chicken cholera to the two academies. The following week he submitted the second paper, titled, “The Extension of the Germ Theory to the Etiology of Some Common Diseases.” *  The latter gave some very detailed observations on the microbes he had found in three cases of boils, seven cases of childbirth fever, and one of osteomyelitis, a serious bone disease.

Most of the maternity cases he cited were patients of Dr. Hervieux, the physician whose lecture he had interrupted the year before. Although Hervieux still disagreed with Pasteur’s theories, the physician had allowed him to collect samples of blood and pus from sick mothers. Now Pasteur gave as his opinion that childbirth fever was actually several different diseases, each caused by a different microbe. Once again he urged the medical members to guard against these ailments by taking antiseptic precautions.

As for the osteomyelitis case—Pasteur reported that he had discovered in pus from the diseased bone the same characteristic microbe that was swarming in pus from the boils. Accordingly he suggested that boils and osteomyelitis were two forms of the same disease—that osteomyelitis was, so to speak, a  “boil of the bone.” A wildly farfetched theory this seemed, indeed—for a chemist to advance to respectable physicians—yet later research by scientists proved that it was true.

Pasteur realized perfectly well that he was courting trouble from the medical men by this new intrusion in their field. But he was desperately eager to push ahead just as rapidly as possible in the conquest of man-killing diseases. Therefore—he now explained in his paper—he was offering his studies on boils and childbirth fever “in their present form— such as it is” only “in my desire to see them completed by those who might be tempted into activity on them.” He continued, “I have presented the facts as they appeared to me and I have ventured interpretations of them” but in the field of medicine, Pasteur acknowledged, it would be easy for him to have a prejudiced viewpoint. “I do not forget, either,” he repeated, as he had on similar occasions, “that medicine and the veterinary art are strange to me.”

Pasteur’s conciliatory language was wasted—his papers triggered a sharp new attack against him in the Academy of Medicine. It was led by Jules Guérin, a dignified seventy-nine-year-old surgeon who was no relation to Pasteur’s friend, Alphonse Guérin. Guérin and several other members had been listening with growing anger to this impudent chemist who sometimes spoke so tactlessly of the “old medicine” as contrasted with the germ theory of disease. Just three months earlier, Pasteur had dared to suggest that his discovery of a chicken cholera vaccine might point the way to the prevention of typhoid fever and measles. Now—even more outrageously—he was lecturing the physicians on the cause of boils and how to prevent childbirth fever! This last effrontery was more than Guérin could bear without striking back.

First, Guérin contradicted a statement Pasteur had made —that the exact scientific relationship between smallpox and Jenner’s vaccine was still unknown and might be profitably investigated. When Pasteur stuck to his views, the old doctor exploded.

“Until now I have kept silent on the ideas of Monsieur Pasteur,” he said with indignation. “But the unlimited extension that our colleague wishes to give to his system—which aims at nothing less than toppling our entire science—makes me bound to intervene.” He added wrathfully, “I must speak to defend not only my own work but also what I believe to be the foundations of medicine against the invasion of the germ theory!”

Guérin was defending a lost cause—more and more physicians and scientists were coming to understand and accept the germ theory. But as usual Pasteur felt he had to answer all opposition—and he did. As the weeks passed, supporters of both men joined in the debate. It was a battle memorable even for the Academy of Medicine, which had been the scene of many stormy fights among its hot-tempered members.

The climax came on October 5. By now Guérin had expanded his attack and was demanding that Pasteur reveal how he made his chicken cholera vaccine—if he really had such a thing. This Pasteur refused to do; it was a question of his “scientific honor,” he explained. And thoroughly losing his temper, he burst out, “I am not going to compromise mine by a too hasty publication just to satisfy the indiscreet, untimely, and unhealthy curiosity of Monsieur Guérin!” Infuriated, Guérin jumped up from his seat. He started to make a lunge for Pasteur, but another member held him back and the meeting ended in an uproar. The next day Guérin sent two seconds to call on Pasteur with the mission of formally challenging him to a duel.

Of course a duel was out of the question between the seventy-nine-year-old surgeon and the lame scientist with his paralyzed arm. A flurry of notes passed between friends of the two men and academy officials. Pasteur wrote the academy that he had not meant to offend a colleague. He had thought only of defending the accuracy of his work, he explained. Dr. Guérin stiffly accepted this letter as an “apology” and the matter was dropped.

Just three weeks after this tumultuous meeting, Pasteur presented still another paper to the two academies. With his final tests completed and his doubts satisfied, he disclosed at last—in his own good time—how he had attenuated a culture to make a chicken cholera vaccine.

Notes

* Etiology is the science of investigating the causes of disease. Back

19

Victory at Pouilly le Fort

LOUIS PASTEUR did not let the feud with Guérin interrupt his great objective—to seek vaccines that could immunize animals and perhaps even human beings against various diseases. As the first step, he decided to concentrate on developing a safe vaccine against anthrax.

He soon learned that even this modest task had its perplexing features. Pasteur began his research by trying out on anthrax microbes the same attenuation method he had found successful with chicken cholera germs—that is, growing them in a culture exposed to the air. Unfortunately, as the anthrax bacilli grew in the culture flasks, they developed into the tiny balls called spores. The tough little spores, which could live for years without food or water, were not at all weakened by long exposure to the air. When they changed again into bacilli, these bacilli proved to be as deadly as ever.

His first job, then, was to keep the spores from forming.

For months Pasteur struggled with this problem, growing the bacilli under all sorts of living conditions. He finally found his answer by keeping the cultures at a very carefully controlled temperature.

He learned that if he heated the bacilli to 45°C. (ii3°F.) they stopped growing entirely. If he kept them at a slightly lower temperature—42^0C. to 43°C.—they could grow and multiply but would not change into the spore stage.

Accordingly he allowed his cultures to grow at 42°C., keeping them in shallow layers where they would have plenty of contact with the air. After a week or so of this treatment, the anthrax bacilli became weakened just as the chicken cholera microbes had been.

By more patient experimentation, Pasteur learned how to control the attenuation so that he could produce anthrax bacilli with just the degree of virulence he wanted. For example, if he exposed a virulent culture to the air for ten days, it would give sheep a mild case of anthrax but would not kill them.

He then worked out a system of vaccinating a sheep in two steps. First he inoculated it with a very weak culture. Twelve days later he injected it with more virulent microbes. After these two inoculations, the animal was protected even when it was injected with a very virulent culture that quickly killed unprotected sheep.

“What will happen,” Pasteur began to wonder, “if I let my attenuated microbes go through the spore stage? Will bacilli grown from these spores be as weak as their parents were—or will they be virulent?”

He experimented and was encouraged to find that his attenuated microbes kept their initial weakness even when they were allowed to go through their normal cycle and develop spores. Thus, when he had once attenuated the microbes, he no longer had to keep them at 42°C. He could let them develop spores and in this form they could easily be transported and kept until used.

In February, 1881, Pasteur announced to both academies his method of protecting sheep against anthrax by preventive inoculation. So far, he said, he had tested the method only in the laboratory but in the spring he hoped to try it out on a farm.

His announcement brought a quick reply from a veterinary surgeon named Rossignol, who served as an editor of the Veterinary Press. “Monsieur Pasteur’s discovery, if it were genuine, should not be kept in the laboratory,” Rossignol wrote in his paper. He would be delighted to arrange a field trial, he added, and he started a campaign for contributions to pay for test animals and expenses. Soon money began to roll in from hopeful farmers. Rossignol placed the project before the agricultural society of Melun, a town southeast of Paris. The society agreed to sponsor it.

The scientist accepted Rossignol’s invitation against the advice of all his friends. It was risky to make a big field trial so soon—with so much fanfare and publicity! The whole subject of microbes was widely regarded as rather a humorous matter—dozens of jokes were being circulated about them. If the test failed, Louis Pasteur would be the laughingstock of Europe.

No one knew better than Pasteur himself how much of a risk he was taking. Rossignol was no friend; in fact, he had written some very unpleasant things about Pasteur and the germ theory of disease. It seemed plain enough that the editor expected the test to be a huge failure.

But what a chance to tell the story of anthrax vaccination not just to a few scientists—but to all French farmers and to millions of other people! Besides, by this time Pasteur was confident of winning a victory. “What succeeded in the laboratory on fourteen sheep will succeed just as well at Melun on fifty,” he told his worried friends.

He worked out careful plans for the test program, to be held at a farm called Pouilly le Fort, near Melun. Sixty sheep were to be put at his disposal. Twenty-five sheep would be vaccinated by means of two inoculations, given twelve days apart. Then these and twenty-five unvaccinated sheep would be inoculated with a deadly anthrax culture. Their condition would be compared with that of the final ten sheep which would receive no injections at all. Several cows and an ox would also be inoculated since cattle sometimes caught anthrax, too, although they were less apt to die of it.

The first inoculation was scheduled for May 5. When Pasteur reached the farm he found a big crowd waiting—farmers, veterinarians, physicians, scientists, public officials, and curious onlookers. They followed him toward the little shed where the test animals were waiting. As the crowd watched, Roux and Chamberland inoculated each animal with five drops of a culture of weakened germs.

During the following days the young men went regularly to the farm, to take the temperature of their patients and keep close watch on them. After twelve days they injected the second, more virulent culture. The animals did not seem to be disturbed at all by these doses.

May 31 was the day set for the big test—the inoculation of both vaccinated and unvaccinated animals with a very virulent culture. By now all France was excited and several thousand people made the trip to Pouilly le Fort. Among them was the Paris correspondent of the London Times, ready to spread news of the great experiment around the world. Also present was Pasteur’s old enemy, Colin, who remained as suspicious as ever.

Colin thought he saw the possibility of some cheating by Pasteur. He gave a warning to Biot, a veterinary surgeon who was supervising the test.

“Watch the broth containing the virulent culture,” Colin advised. “The anthrax germs are heavy and will settle to the bottom of the broth. Pasteur will inoculate the vaccinated animals first; they will get the top part of the broth, which is harmless. Then he’ll use the bottom part of the culture to inoculate the unvaccinated animals. Of course it will kill them since that is where the germs have settled.

“So, just before he uses the culture, give the bottle a good shaking to distribute the germs evenly.”

Biot did not forget Colin’s warning. He not only shook the bottle; he insisted that the animals be given three times as big a dose of virulent germs as had originally been agreed upon.

By half past three in the afternoon the injections were finished and Pasteur went back to Paris. There was nothing for him to do now but wait.

The next day Roux and Chamberland went down to the farm to check on their patients. They reported to Pasteur that some of the unvaccinated sheep were very sick; they stood with drooping heads and refused to eat. All of the vaccinated sheep, with one exception, were eating normally. Some were running a temperature, however, and the one with no appetite had a fever of 40°C. (104°F.).

Later that day came still more alarming news in a telegram from Rossignol. “One of the vaccinated sheep is dying,” he announced.

Suddenly Pasteur’s wonderful self-confidence deserted him. All his hopes and plans seemed to come crashing down; he was sure the test would be a gigantic failure. In vain did Madame Pasteur try to reassure him. He spent a sleepless night.

At nine o’clock the next morning a very different telegram arrived from Rossignol. All the vaccinated sheep were well, including the one that had seemed to be dying. All the unvaccinated animals were either dead or dying. The telegram ended with the words: “Stunning success!”

When Pasteur and his party reached the farm that afternoon, a great cheer went up. Enthusiastic representatives of agricultural, veterinary, and medical societies crowded about to shake his hand. Newspapermen sought interviews. Even the skeptics, Biot and Rossignol, congratulated him warmly.

In the field the dead bodies of twenty-two unvaccinated sheep lay side by side; when two of these were examined, their blood was found to be full of anthrax bacilli. The rest of the unvaccinated sheep were dying. The unvaccinated cattle were very sick, although they eventually recovered. In startling contrast, all of the vaccinated animals were in perfect health.

Pasteur had scored a complete victory. He had won his big gamble.

20

Crowded Years

APPEALS FOR HELP, in fighting disease were now pouring in on Pasteur from all over the world. The day after his triumph at Pouilly le Fort, he was asked to go to South Africa to study an epidemic raging among goats.

Madame Pasteur wrote to Marie Louise, “Your father would like to take that long journey, passing through Senegal on his way to collect some good germs of yellow fever. But I am trying to moderate his enthusiasm. I consider the study of rabies enough for the present.”

The scientist had begun his investigation of rabies six months before. But this work was beset by unexpected stumbling blocks and long weeks of waiting for the results of experiments. It would, in fact, take Pasteur four more years of work before he mastered all the difficulties.

Meanwhile, since he now had assistants to do the slow, routine part of the research, he certainly had no intention of limiting himself to rabies alone—which his wife knew very well. He was “at the boiling point” as he himself put it—full of ideas and bursting with energy. And why shouldn’t he be feeling elated ? Thirteen years before in the dark days of his heart attack, he had lamented dying because he wanted to do so much more for his country. Now he found himself the discoverer of a new technique to outwit disease—not just by curing it but by preventing it—and he had already demonstrated its possibilities by developing two successful vaccines!

The period between the Pouilly le Fort test and his final victory over rabies was one of the busiest of Pasteur’s busy life. His schedule would have exhausted many a younger and stronger man—and he was now fifty-eight. He still grew very tired and his left hand and arm were still so paralyzed he had to call for help when he wanted to manipulate laboratory apparatus. But he would not stop his work or consent to rest for long; there was too much to do.

Along with his rabies research, he carried on projects to develop two new vaccines for farm animals and did much supplementary work on anthrax. Farmers were clamoring for vaccine to save their flocks and he had to arrange hastily for its production on a large scale. He also conducted further experiments to improve his vaccination techniques and made many more field tests to convince critics who still claimed the vaccine was a failure.

In addition, he made speeches at international gatherings and at celebrations in his honor. While he naturally enjoyed the recognition that was coming his way, he had serious reasons for taking precious time from his laboratory for these public appearances. He was shrewd enough to know that honors could be potent weapons in his crusade against disease—people were much more apt to pay attention to the words of the famous Louis Pasteur than to those of some obscure scientist in an out-of-the-way laboratory. And when he acknowledged an award or a tribute, he always did so in the name of science—for he believed that in cheering him, the public was acquiring new interest in and respect for science and the things scientists could accomplish.

Pasteur also kept the scientific societies up to date on his research. During the week of June 13, 1881, shortly after the Pouilly le Fort test, he appeared on three consecutive days before the Academy of Sciences, the Academy of Medicine, and the Agricultural Society to report on his anthrax vaccine. Most of the members gave him generous applause but at the Academy of Medicine, an old adversary arose with a question. “I should like to ask Monsieur Pasteur,” said Colin smoothly, “why he used a culture of bacteria to test the effectiveness of his vaccine, instead of using anthrax blood itself.” Colin made it clear that he thought the vaccine could not protect an animal against the blood of a diseased sheep.

Pasteur retorted with disgust, “Very well, if you like, inoculate the sheep and cows at Pouilly le Fort with the most virulent anthrax blood you can find. I tell you they will notice nothing!” To prove his point, he made a new test which showed conclusively that vaccinated sheep withstood a strong injection of anthrax blood just as well as they did a culture of virulent germs.

That same June, he also campaigned to get the red ribbon of the Legion of Honor for Roux and Chamberland. Pasteur had always been punctilious about giving public credit to the young men who had worked with him on various projects. Now he himself had been offered the Grand Cross, the highest of the five decorations of the legion, but he refused to accept it unless his assistants were honored, too.

All three scientists were in their laboratory when a friend brought word that the young men would indeed get the ribbon. Madame Pasteur wrote her daughter, “Hearty congratulations were exchanged in the midst of the rabbits and guinea pigs.”

At the end of the month Pasteur notified the secretary of the French Academy that he was a candidate for membership. Of all organizations in France, this academy was the most famous and important. Founded in 1635, it had forty members who were known as France’s “immortals,” including writers, scholars, soldiers, artists, statesmen. A new member could be admitted only on the death of an “immortal.”

Two years earlier several members of the great academy had urged Pasteur to seek the seat of a member who had died, but the scientist had declined; too many other outstanding sons of France were candidates. Now another seat had become vacant with the recent death of Emile Littre, a distinguished philosopher and editor of a dictionary. Since Pasteur’s friends were pressing him to be a candidate and the whole country was shouting his name in a wave of enthusiasm, he decided to seek admission to the academy—even though he might very possibly be rejected. “What does a defeat matter?” he wrote cheerfully to his son-in-law, Rene. “On the contrary, I’d find it a good excuse to stop thinking of that academy and its speeches.”

Once he had made up his mind to be a candidate, he put the same energy into seeking votes that he did into hunting a new microbe. He wrote discreet letters to academy members whom he knew, to find out how much support he could count on. Just to be prepared, Madame Pasteur began pasting into a scrapbook all the articles on Littre that were then appearing in magazines and newspapers. According to custom, if Pasteur won he would be expected to give a speech on the philosopher’s life and work.

In August Pasteur went to the International Congress of Medicine in London as an official representative of France. When he entered the crowded hall with his son and son-in-law, there was a great burst of handclapping and cheering.

“We should have come earlier,” Pasteur said a bit nervously. “No doubt the Prince of Wales is arriving.”

“Monsieur Pasteur, it is you they are cheering,” replied Sir James Paget, president of the congress.

A reporter for a French newspaper wrote, “Pasteur was the greatest success of the congress.” He dined at the lord mayor’s residence and attended a luncheon where he was congratulated by the Prince of Wales and the Prussian Crown Prince. Whenever a speaker at a meeting mentioned Pasteur’s name—which was often—the audience applauded vigorously. He accepted an invitation to explain his attenuated vaccine at a general session although, as he told the medical men, he had come to the congress merely to listen and “to instruct myself.”

While still in London he wrote Marie how proud he was that a Frenchman should have received such acclaim “in that immense assemblage of foreigners—especially of Germans who are here in much greater numbers than the French.” Pasteur had not forgotten his country’s humiliating defeat in the Franco-Prussian War.

In September he went to Bordeaux in search of the yellow fever microbe. Ships had been arriving from Senegal with victims of an epidemic, but when he reached the port he learned that the sick people had either died or were recovering. Another ship was due in ten days, however, so Pasteur decided to wait for it. He made elaborate plans for the examination of patients with as little risk of contagion as possible.

“In the meantime, what shall I do in Bordeaux?” the restless scientist wrote to his wife. He explained that he had made friends with the keeper of the town library; it was open to him at all hours. “I am there now,” he reported, “alone and very comfortably seated, surrounded with more books by Littre than I can possibly get through.”

Although the election for the French Academy was not due for several months, Pasteur was now sure he had enough votes to win. He had taken the scrapbook about Littre with him to Bordeaux and was taking advantage of this rare stretch of free time to begin composing his speech.

When the ship from Senegal finally arrived, he found that its only victim of the epidemic had died and been buried at sea. Since his last chance to hunt the yellow fever microbe was now gone, the disappointed investigator went back to Paris.

In December Pasteur was elected to the French Academy with twenty votes out of the thirty-three cast, and the following April he was received into membership in a brilliant ceremony. Dressed in a green, gold-embroidered uniform, with a sword at his side, he gave his speech on Littre before a crowd of celebrities and his own happy family.

French towns that had benefited from his research were now vying with each other to stage celebrations in his honor.

The Melun Agricultural Society presented him with not just one medal but three—of gold, silver, and bronze—for his anthrax vaccine. Aubenas, the town where France’s silk industry had been founded three centuries before, awarded another medal to Pasteur for his silkworm research which had saved their industry from ruin. And at Nimes and Montpellier he made still more speeches, went to banquets, and conducted new tests of his anthrax vaccine.

When he went to Arbois in August of 1882, he kept up the same energetic pace. Again he was making changes in the little tannery building. He needed space for a billiard table— since he enjoyed the game—and more room for the friends and relatives he liked to have visit him. The nursery Pasteur had built two years before was now occupied by a granddaughter, Camille.

Besides supervising the remodeling, he mailed a steady stream of directions to Roux on the rabies experiments and to other assistants on a new microbe-hunting project he had undertaken. The Melun Agricultural Society had appealed to Pasteur to find a safe vaccine for pleuropneumonia, a serious disease of cattle. Experimenters had already tried to protect animals by giving them a mild case of pleuropneumonia but—as had been true with anthrax—these “mild” doses were treacherous and often turned virulent.

With ten thousand francs donated by the society, Pasteur bought thirty head of cattle and a dozen horses for experimentation and installed them on a farm in the woods at Vincennes. He made some progress but the research proved to be too discouraging and time-consuming and he eventually gave it up to concentrate on rabies. Fifteen years later Roux and other scientists did develop a successful pleuropneumonia vaccine.

From Arbois Pasteur went to Geneva, Switzerland, where he had been asked to speak before the International Congress of Hygiene. He had taken special pains with his speech because one of his listeners would be Robert Koch, the German bacteriologist who had first proved that the rod bacteria were the cause of anthrax. Koch and his assistants had been belittling Pasteur’s research on anthrax and claiming there was no such thing as an attenuated vaccine. Pasteur’s results, they said, were probably brought about by some adulteration of his cultures or by the deposit of a strange germ on the needle during the inoculation.

When Pasteur addressed the congress, he invited Koch to discuss the criticisms that the German had made of Pasteur’s work. Koch declined. He would answer later in writing, he stated.

In November Pasteur went to a farming region near Avignon to hunt a vaccine for swine fever, a disease which had recently killed many thousands of pigs in France and abroad. The scientist was accompanied by two assistants, Louis Thuillier and Adrien Loir, Pasteur’s nephew, who had recently joined the laboratory.

Previously Thuillier had discovered the microbe of swine fever and had learned to grow it in a culture. The next step was to find a way of attenuating the culture so a vaccine could be produced. Pasteur first tried weakening the germs by exposing them to the air, as he had done with chicken cholera and anthrax microbes. When this method proved unsatisfactory, he worked out another ingenious way of attenuating the microbes—by growing them in the bodies of rabbits!

Among his many experiments, he had tried injecting a virulent culture of swine fever microbes into rabbits. The microbes grew and multipled in the rabbits’ blood, quickly killing them. But in some strange way, this cultivation inside the rabbits seemed to weaken the microbes—to make them less deadly for pigs. And when Pasteur injected a culture of these weakened microbes into a second rabbit, he found out that their descendants were weaker still.

Accordingly he learned to attenuate the microbes by growing them in a series of rabbits, one after another. Through this process the germs became so weak that when he injected a culture of them into a pig, it did not get sick. The same pig then easily withstood an injection of virulent microbes, showing that it had been successfully immunized.

He worked on swine fever in the Avignon region until early in December and then took some pigs back to Paris with him for further tests.

That same month Pasteur received Koch’s reply to his Geneva speech, which had been published as a severely critical pamphlet. Koch now acknowledged that Pasteur had, indeed, developed a vaccine by attenuating cultures of microbes and he declared that the principle of an attenuated vaccine was an important discovery. But in the case of anthrax, Koch added, the effect of a vaccine did not last long enough to make it worth while. He also reported that he had bought some of the vaccine in the open market and found it full of impurities.

Pasteur’s supporters maintained that Koch, twenty-one years younger than the French scientist, was simply jealous of Pasteur’s success in developing a preventive treatment for anthrax. However, Koch was a brilliant and conscientious investigator and he was doubtless right in saying that there were foreign microbes in the anthrax vaccine he had purchased. Although Pasteur himself took infinite pains to keep his cultures pure during experiments, the anthrax vaccine on the market was not always a pure culture. Chamberland, who was in charge of producing it, sometimes added a few hay bacilli in an attempt to stabilize its strength. And in the rush to produce enough vaccine to meet the demand, a stray microbe might have slipped into the bouillon that served as a culture medium. The solid medium which had recently been developed by Koch made it much easier to keep cultures pure.

Pasteur did not claim that his vaccine always prevented death from anthrax and his own tests showed that the immunity of a vaccinated animal did not last indefinitely. He recommended that, for safety, the vaccination should be repeated each year. But yearly vaccinations were not needed very long. The vaccine helped farmers to get anthrax under control so their flocks were protected from contagion. Vaccination could be kept as a reserve weapon in case a new epidemic broke out.

During December Pasteur worked on a long reply to Koch, which appeared as an open letter in a French publication. He gave figures comparing deaths from anthrax before and after his vaccine discovery. For example, in one district where 79,392 sheep had been vaccinated, an average of less than one vaccinated animal in one hundred had died during the year. In the same district, the annual death rate for the ten years before vaccination had been more than nine sheep per hundred.

The year of 1883 brought Pasteur new recognition—and a tragedy. First, the grateful French government voted to raise his annual pension from 12,000 francs to 25,000, and later, in July, he attended a ceremony in the little town of Dole, to see its proud citizens dedicate a plaque on the house where he had been born. Then with September came the grim news that one of his assistants, Louis Thuillier, had died suddenly of cholera in Egypt.

Pasteur was shocked and grieved; it was he who had dispatched the French mission to try to track down the cholera microbe during the epidemic that was then devastating Egypt. He had been very fond of Thuillier, and although the young man had volunteered for the mission, Pasteur blamed himself bitterly for having sent Thuillier to his death.

Vaccinating a sheep to protect it from anthrax

But he had to keep on with his vital work. By now he had overcome many of the difficulties in his rabies study and was concentrating more of his time on the search for a vaccine. During the twelve months following the Dole celebration, Pasteur seldom left his laboratory for speeches and he represented France only once at an international gathering—the three hundredth anniversary of the University of Edinburgh in Scotland.

By May, 1884, he had progressed far enough to ask that the Academy of Sciences appoint a commission to investigate his rabies vaccine and check on his results. As it happened, the same month brought the anniversary of another event highly important in Pasteur’s life—although in the excitement of getting the vaccine tests under way, he very possibly never gave it a thought. His faithful Marie did not forget, however. On May 29 she wrote to Marie Louise and Rene:

“The commission met today and elected Monsieur Bouley as chairman. Nothing is settled as to commencing experiments. Your father is absorbed in his thoughts, talks little, sleeps little, rises at dawn and, in a word, continues the life I began with him this day thirty-five years ago.”

21

Taming an Invisible Killer—the Rabies Virus

BY MAY 1884, when Pasteur could report his first definite success in developing a rabies vaccine, he had already been laboring on this problem for more than three years. But his abhorrence of rabies could be traced back much further in his life—to the time in his boyhood when his Arbois neighbors had died in agony from the bite of a mad wolf. More than fifty years had passed since then—and still the physicians and scientists had made no real progress in learning how to save a rabies victim.

The course of the disease was confusing and unpredictable.

The only treatment which seemed to have any value was the painful one that young Louis had witnessed at Arbois—the cauterizing of a bite by burning away the flesh in the area of the wound—but even this drastic remedy often failed. Victims might not develop rabies until many weeks or even months after they had been bitten. On the other hand, people who received no treatment at all after a bite from a mad dog often stayed perfectly healthy.

One fact was certain—no one ever recovered from an attack of rabies. After the acute symptoms began to appear, death was sure to follow. Sometimes it came more speedily because the unfortunate victim was smothered between mattresses by his terrified family who believed his breath might be contagious.

This strange illness had been feared by ancient peoples, too—it was the Romans who gave it the name rabies, a Latin word meaning “rage” or “madness.” In English it has been popularly known as hydrophobia, meaning “fear of water,” because human victims often have gone into convulsions when they tried to take a drink. But since mad animals do not have this same fear of water, rabies is the more accurate term for the disease of both animals and human beings.

In the Paris of Pasteur’s day, one man who had been searching for a remedy was an army veterinary surgeon named Bourrel. He had even tried the impractical idea of filing down the teeth of dogs so they could not bite into the skin. In December, 1880, with the hope that the famous Louis Pasteur could throw some light on the subject, Bourrel sent two mad dogs to the scientist’s laboratory at the Ecole Normale.

Pasteur began the study in his usual way—trying to track down a guilty microbe. He searched particularly in the animal’s saliva. Investigators had already suspected that the cause of rabies might be hidden there, since the disease was transmitted by bites.

In a hospital Pasteur gathered some mucus from the mouth of a little girl who had just died of rabies. Diluting this with water, he injected the mixture into some rabbits, which died within thirty-six hours. Saliva from the dead rabbits was then injected into healthy rabbits, and these died almost as quickly.

Under his microscope Pasteur examined the blood and saliva of his dead rabbits, as well as saliva from persons who had died after being bitten by a mad dog. In these specimens he thought he detected the killer—a tiny microbe that was new to him, shaped like a figure 8. Through long experimentation he learned to grow this microbe in veal broth. When he injected a culture of it into rabbits, they died quickly and the same tiny microbe could be found in their blood.

But the fact that he had killed rabbits with his new microbe did not prove it was the cause of rabies. Had his animals truly died of rabies—or of some other disease? In an attempt to find out, Pasteur examined samples of saliva from healthy people and from patients with other diseases. There was the same little figure-8 microbe! At that early stage in the science of microbiology, Pasteur did not know what it was—but from his detailed description, scientists today are sure that he had spotted the germ causing lobar pneumonia. It is often present in the mouth and ordinarily causes no trouble in a healthy person.

Of course Pasteur was disappointed at having wasted so much time and labor on a false trail, but he was not discouraged. Again he took up the hunt for the rabies microbe.

He searched in the saliva, the blood, and the tissues without success. After several more months of fruitless work, he very sensibly decided to give up this line of study. “Perhaps rabies is caused by a virus that cannot be seen in my microscope,” he speculated.

Then Louis Pasteur took another great pioneering step in microbiology. Instead of giving up the fight against rabies, he went right ahead trying to defeat a virus that he could not see—that he could not even be sure existed! At that time, the term “virus” had not acquired the meaning it most commonly has today—that is, a microbe so tiny it is ordinarily invisible under the lens of a regular microscope. Virus is a Latin word for a “slimy liquid” or “poison,” and the scientists of Pasteur’s day thought of a virus in just that way —as a vague poisonous “something” in the fluids or tissues of the body, which could carry disease from one human being or animal to another.

Pasteur himself suspected that the “poisonous” effect in a disease such as rabies might be caused by microorganisms infinitely smaller than the bacteria he was familiar with. But he never saw the microbes we call viruses—and neither did anyone else until some years later. With a very few exceptions, viruses are so small they can be seen only through the powerful electron microscope.

In pursuit of this unknown, invisible virus, he went back to the slow, uncertain process of trying to give his test animals rabies with injections of saliva or by means of the bite of a mad dog from Bourrel’s kennels. Pasteur risked death himself in these experiments. Once he drew saliva from the mouth of a mad bulldog through a glass tube held between his lips, while two of Bourrel’s attendants held the raging, struggling beast down on a table.

Sometimes his bitten or injected animals developed rabies; often they did not. Pasteur might have to wait several months before he knew whether or not he had a new rabies subject for study, since there was such a wide variation in the length of time before the disease showed up (called the period of incubation). Naturally this long waiting period slowed up his research.

He racked his brains trying to figure out a surer way to give rabies to dogs and rabbits. Like other observers, he had noticed that the disease seemed to affect an animal’s nervous system. “Perhaps,” he thought hopefully, “the virus concentrates in the brain and I can find it there more easily.” Accordingly he removed some of the matter from the brain of dogs that had died of rabies—taking care to avoid contamination of it—and injected it under the skin of several rabbits. In almost every case the animals became rabid.

Although this was encouraging progress, Pasteur still frequently had to wait many weeks before his animals developed the disease. Why—he pondered—should the period of incubation be so long? He theorized, “Perhaps the virus does not find a good place to grow and multiply until it reaches the central nervous system. When a bite is on an arm or a leg, then the virus has an especially long distance to travel. I might be able to speed up the appearance of the disease if I could inject rabid matter directly into the brain.”

But how could this be done ? His assistant, Roux, drew on his medical training to suggest a method.

“It is called trepanning,” Roux explained. “We will give a dog an anesthetic so it won’t feel any pain. Then we can cut a small hole in its skull with a surgical saw. We’ll inject the rabid matter directly into its brain and close up the hole in its skull again.”

Pasteur makes notes on the condition of rabbits used in his rabies experiments.

He wore a little skull cap when working in his laboratory.

Pasteur shook his head. Although he claimed not to be fond of animals, his assistants knew how tenderhearted he was. He never let an animal suffer unnecessarily, but always used anesthetics for operations and always put his rabid animals to sleep permanently as soon as he had finished his observations of them. The very thought of cutting a hole in a dog’s skull repelled him—why, it could not help but be painful! He would not allow it.

There the problem rested until one day when Pasteur was absent from the laboratory. Roux, convinced that his method was the only solution, chloroformed a dog and trepanned it. Into its brain he injected some matter from the brain of a dog that had died of rabies. When Pasteur returned, Roux told him about the operation.

“Oh, the poor animal!” cried Pasteur. “Where is it? Its brain is certainly wounded; it must be paralyzed.” In answer, Roux brought up a lively little dog that was wagging its tail, obviously not at all bothered by the hole in its head. Yet two weeks later the little dog showed the first signs of the fatal rabies.

Pasteur was relieved and reassured to learn that trepanning was not painful, and from that time on it became a regular practice in his laboratory. Producing rabies in a test animal only two weeks after inoculation proved to be a big advance, for it speeded up the research program.

Soon afterward the scientist discovered how to make the period of incubation still shorter. He took some matter from the brain of a trepanned dog that had died of rabies and injected this into the brain of a second dog, which became rabid in less than two weeks. Then he transferred a bit of matter from the brain of the second dog to the brain of a third dog, thus shortening the period of incubation still more.

Finally he was able to produce rabies in an animal only six days after its inoculation. This seemed to be the limit, however. No matter how many times he made the transfer from one brain to the next, he could not shorten the period of incubation to less than six days.

With these experiments Pasteur had done more than speed up his research—he had opened a new chapter in the history of microbiology. He had demonstrated that an invisible virus could be tamed and grown in a culture for study and use—just as he had once shown how to “domesticate” yeast cells and bacteria. But viruses are much more difficult to raise than bacteria and not only because they are so small. Viruses refuse to grow in ordinary liquid or solid culture media; they demand a nutrient medium that is still alive— such as the cells of a living animal.

Pasteur, of course, had no way of knowing that his rabies virus needed living cells to flourish—he simply found out through many futile experiments that it would not grow in flasks containing blood, fresh nerve tissue, or any other nutrient medium he could think of. So—he discarded his flasks and used the brains of live rabbits as his culture medium! Not only did the rabies virus grow and reproduce itself in this favorable medium, but its “children” proved to be even more virulent than the “parent”—they could produce rabies more quickly. Thus—by growing his culture in the brains of a series of trepanned rabbits—Pasteur could increase its virulence to the point where it would almost certainly produce rabies in an injected animal within six days. He called a rabies culture of this fixed, stabilized strength a fixed virus —a term used by microbiologists today.

But the most difficult job still lay ahead. How was Pasteur to attenuate this invisible virus so that he could make a vaccine of it ?

Many more months of work went into solving this new problem. The most successful method of attenuation was developed from an idea advanced by Roux. Since the rabies virus seemed to lodge in the nervous system, Pasteur experimented with the spinal cord of a rabbit that had died after being injected with a fixed virus.

He suspended the spinal cord in a flask plugged with cotton, taking care that both the flask and the air in it were sterile. Air could filter in through the cotton, but germs were kept out. In the bottom of the flask was a layer of potash to keep the air dry, because moisture would have caused the cord to putrefy. In this dry air, the rabies virus in the spinal cord gradually weakened and became less and less virulent.

Pasteur learned by much experimentation that if he let the spinal cord dry for fourteen days, the virus in it still remained alive but was too weak to give rabies even to rabbits or other small animals. It was this greatly weakened culture which he used as the first step in his method of vaccination.

After the cord had been drying fourteen days, he cut off a short section of it. He crushed it, mixed it with pure water and injected it under the skin of several dogs. The next day Pasteur inoculated the same animals with a bit of cord that had been drying only thirteen days. The following day he used a cord that had dried just twelve days.

This process he continued daily—each day inoculating the dogs with a cord that was slightly more virulent because it had been drying for a shorter period of time. At the end of two weeks, Pasteur used the cord of a rabbit that had died the same day. He knew from experience that this very virulent material would almost certainly kill an unprotected animal within a week. Yet when he inoculated his vaccinated dogs with it, they showed not the slightest sign of rabies.

Then Pasteur tried putting several of these vaccinated dogs in cages with mad dogs. Even when his treated animals were badly bitten, they did not develop rabies. He also tried injecting the deadly virus directly into the brain of his vaccinated animals. They withstood this extremely virulent injection just as easily as they did the bite of a rabid dog.

At last Louis Pasteur had found what he was seeking—a vaccine against rabies!

By the summer of 1884 the news of his discovery was starting to spread throughout the world. Articles on his rabies research were being published in many foreign lands as well as in France. In August Pasteur himself reported on his vaccine before the International Scientific Congress at Copenhagen. And that same month the commission that had been appointed by the Academy of Sciences to test the vaccine issued an enthusiastic report on it and recommended that Pasteur be given new, larger kennels where he could conduct further experiments.

For Pasteur had not finished his rabies research—there was another important problem he wanted to investigate. Could an animal be saved after it had been bitten? Certainly the experiment was worth trying. Since the period of incubation after a bite was so long, it might be possible to build up an animal’s immunity before the virus could reach the central nervous system and kill it.

This theory Pasteur tested by allowing a pair of healthy dogs to be bitten by a mad dog. One of the pair then received the series of protective inoculations; the other received no treatment. The scientist tried this experiment repeatedly and found that while the untreated dog in a pair often developed rabies, the vaccinated animal did not.

He had made another tremendous advance. Now Pasteur knew that if he started his series of vaccine inoculations soon enough after a dog had been bitten, he could save its life.

One great question remained—could the lives of human victims of mad dogs be saved, too? Pasteur did not lack opportunities to find out, for he was now receiving desperate letters from people who had been bitten by rabid animals and who begged the scientist to treat them with his inoculations.

Reluctantly he refused all such pleas. He explained the reason in a letter written toward the end of September to the Emperor of Brazil. Pedro II and Pasteur had met more than ten years earlier and had been corresponding since then. The Emperor was much interested in science; in fact, he had visited Pasteur’s laboratory during a trip to Paris and had presented the Frenchman with Brazil’s highest decoration.

Pasteur wrote, “Until now I have not dared to attempt anything on men, in spite of many opportunities and my confidence in the result. I am too much afraid that a failure now would endanger the future. First, I want to pile up more successful cases on animals. . . . But even then I think my hand will tremble when I go on to mankind.”

Yet he had a suggestion for His Majesty. “If I were a king, an emperor, or even the president of a republic,” he wrote, “this is how I would exercise my right of pardoning criminals condemned to death.” He would give the prisoner a chance to save his life by volunteering for a test of the rabies vaccine. Pasteur added, “I attach so much importance to these measures that, if Your Majesty shared my views, I would willingly come to Rio de Janeiro in spite of my age and the state of my health, in order to undertake such studies.”

Emperor Pedro politely refused the offer. The death sentence had not been employed in Brazil for several years, he explained.

In the spring of 1885 Pasteur arranged to move some of his test animals into larger kennels at Villeneuve l’Etang, near Paris. A small room was furnished for him in one of the buildings, since he wanted to keep a close check on the experiments. By this time, so many successful inoculations had been completed that he wrote to his friend, Jules Vercel, I have a great desire to start with myself—that is, to inoculate myself with rabies and then to stop the consequences, for I am beginning to be very sure of my results.”

Still, he hesitated. In June the mayor of Levier, a town near Arbois, wrote asking him to treat a father and his boy who had been bitten by a rabid dog. “I very much regret that I cannot tell you to send these persons to me,” Pasteur replied. “My research is not yet at the point which would permit me to act on man.”

Within a month he would be forced to act in spite of his misgivings.

22

How Pasteur Saved the Life of Joseph Meister

ON JULY 6, 1885, the bell rang at the door of Pasteur’s laboratory. A man and woman with a frightened nine-year-old boy asked to see the scientist. When he learned why they had come, he went to them at once.

The visitors came from a little town in Alsace. The boy, Joseph Meister, had been attacked by a mad dog two days earlier on his way to school. Before he was rescued, he had been bitten fourteen times on his arms, legs and body.

With Joseph were his mother and the dog’s owner, Theodore Vone, who himself had been bitten on the arm. The travelers had come to Paris on the advice of their doctor in Alsace, who had read about the discovery of a rabies vaccine. But since the doctor had not known Pasteur’s address, the weary little party had gone to several hospitals before they found someone who could direct them to the laboratory at the Ecole Normale.

Pasteur examined the bites of the man and the boy. Vone’s wound was very slight—his shirt sleeve had not even been torn—so the scientist felt reasonably sure that the deadly virus had not entered his body. “Go back home. You will be all right,” Pasteur assured him.

Joseph s condition, however, was much more serious—he had very deep, slashing wounds from the dog’s teeth. His doctor had used carbolic acid on the bites, a treatment that had not proved very effective in the past. Moreover, this doubtful treatment had not been given until twelve hours after the dog’s attack—twelve important hours during which the deadly virus could gain a foothold in the boy’s body.

Louis Pasteur faced a terrible responsibility. If he should treat Joseph with his vaccine—still untried on human beings—and the boy later died, many people would call him “Murderer!” This same thought had deterred him only three weeks before, when he had refused to treat the father and son who lived in Levier. But in that case he had not seen the victims; they were still far away in the Jura Mountains. Now a child’s mother was standing right in front of him, asking for help. He felt he could not tell her, “I am sorry but I will not even try to save your son.”

Instead he said, Come back to the laboratory at five o’clock.” He wanted time to consult Alfred Vulpian, a specialist on the physiology of the nervous system who had served on the commission investigating the rabies research.

Vulpian consented to come to the laboratory to see the boy. After examining Joseph’s many deep bites, he gave as his opinion that, without treatment, young Meister was almost certain to die of rabies. The specialist advised Pasteur to try his vaccine but he refused to give the inoculations himself.

“I am a physiologist, not a practicing physician,” he said.

Pasteur hurriedly sent for Jacques Joseph Grancher, a young doctor who had recently joined his staff. Vulpian and Grancher together decided that no more time should be lost—the first inoculation must be given that night. For the rabies vaccine, they would use a bit of spinal cord from a rabbit that had died after being injected with a fixed virus. The cord had been drying for fifteen days and thus was no longer virulent.

At the sight of these preparations, young Joseph Meister became more frightened than ever and burst into loud sobs. While Pasteur tried to comfort him, Grancher filled a hypodermic needle with a few drops of vaccine and quickly slipped it under the skin of the boy’s abdomen. In a moment it was over—Joseph dried his tears and smiled. After all that fuss, he had felt only one little pinprick! But for the three men, the ordeal had just begun.

Since the Meisters had no place to stay in Paris, Pasteur took a carriage to a store where he bought two iron beds, bedding, and other things they would need. The beds he ordered set up in a building where some of his assistants were living. And he arranged for a woman to cook meals for Joseph and his mother.

Adrien Loir, Pasteur’s nephew who occupied the adjoining room, was assigned to keep a constant watch. Take the boy s temperature four times a day and report to me the slightest change in his condition,” Pasteur told him.

The next morning Grancher gave Joseph the second inoculation, this time with spinal cord that had dried only fourteen days. That same day and the next the boy received two inoculations—then the treatment was cut down to one inoculation a day. Each vaccine was more virulent than the one before.

Pasteur tried to work as usual but he could not keep his mind off his young patient. He went to see the boy at all hours of the day—and even in the middle of the night. When he went to bed he had frightening dreams and often he could not sleep at all. Then he would get up in the dark and go to Joseph’s room. When the child woke up in the morning, he would find Pasteur sitting by his bed, watching him closely.

Joseph himself was having a wonderful time. His bites soon healed and the inoculations did not bother him. He loved to go to the Luxembourg Gardens, with Adrien Loir following at a distance. He played with the rabbits and guinea pigs that were to be used for experiments. His good friend, whom he called “Dear Monsieur Pasteur,” gave him a rabbit for a pet.

Finally Joseph received his thirteenth and last inoculation, with a bit of spinal cord that had been attenuated only one day. Experiments had shown that such a strong vaccine would give rabies to an unprotected animal within a week. Yet the only signs of these last and most virulent injections were several red marks on Joseph’s skin that gradually widened but were not sore.

Pasteur, worn out from the anxiety and suspense, went to stay with Marie Louise and Rene in a quiet house in Burgundy. Every day a telegram arrived from Grancher with the same good news—Joseph was well. The scientist would cheer up for a while. Then he would start worrying about what the next day’s telegram might say.

Eleven days after the final inoculation young Meister and his mother returned to Alsace. Although the boy seemed to be in fine health, Pasteur was still uneasy and anxious about him. Joseph’s physician had promised to report frequently but this did not satisfy Pasteur—he wanted daily bulletins. So he hit on the idea of having Joseph himself send reports on his health. He mailed the physician a package of self-addressed envelopes and money for stamps and asked him to have Joseph write at least every other day. “Just a single word to tell me he’s well, so it won’t interfere with his studies,” Pasteur requested humbly.

And so began a steady correspondence between the famous scientist and the nine-year-old boy. When the mail came Pasteur would seize Joseph’s envelope first, leaving until later all his other important letters from scientists, government officials, or the Emperor of Brazil. Usually Joseph wrote only one sentence: “ I am well.” Once his letter said simply “I’d like to have a rabbit.” That made Pasteur smile. He knew the boy was remembering the fun he’d had with the animals in the laboratory.

A month after the date of the final inoculation, Pasteur wrote, “I am very happy with the good news you give me of your health. You can put a little more interval between your letters, if you wish. Write to me every week or ten days.” And even after all danger of rabies had passed, he kept on sending letters full of fatherly advice and praise. “I received your last letter with great pleasure,” he once wrote, “because I could see that you are making fine progress in writing, spelling, and reasoning.”

From Burgundy Pasteur went to Arbois for the summer. He did not make a public announcement of his successful treatment of young Meister but he did tell a few people about it. One of these was the mayor of Villers-Farlay, near Arbois, who came to call on him.

Soon after the scientist had returned to Paris, the mayor wrote him asking help for another rabies victim, a fourteen-year-old shepherd boy named Jean Baptiste Jupille. He and five younger shepherds had been watching their sheep when a mad dog attacked them. Jupille had faced the fierce animal armed only with a whip in order to give the younger children a chance to escape. The shepherd fought bravely with the finally managing to kneel on it and tie its jaws together with the whip. But in the struggle he was badly bitten on both hands.

Again Pasteur had a difficult decision to make. In Joseph’s case he had been able to start treatment only sixty hours after the boy was bitten. But Jupille was still in Villers-Farlay and before he could reach Pasteur’s laboratory, the rabies poison would have been in his body almost a week. Could the vaccine fight a virus that had had so much time to spread through the human system ?

Pasteur decided to take the risk. He wrote the mayor that he would treat Jupille if the boy came to Paris and his parents gave their consent.

The new series of inoculations proved to be just as successful as Joseph Meister’s had been. On October 26, even before Jupille’s treatment was completed, Pasteur appeared before the Academy of Sciences to report his use of the rabies vaccine on human beings. After he had described his method of inoculation he told the story of the shepherd boy who had saved his companions by his “brave act and his presence of mind.” And as a result, when the members congratulated Pasteur on his achievement they also paid tribute to the young shepherd. One member moved that the Academy of Sciences recommend the award of a prize for heroism to Jupille.

With the news of Pasteur’s discovery, panicky victims of the bites of mad dogs began flocking to his laboratory. He turned none of them away. If they were poor and had no friends in Paris, he found a place for them to stay while being treated.

He quickly set up a clinic for inoculating the patients efficiently. The job of preparing the vaccine was turned over to Eugene Viala, one of his assistants.

Eugene worked in a little room which was always kept at a temperature of 20° to 23°C. (68° to 73°F.). In front of him were rows of flasks plugged with cotton. In each flask, the spinal cord of a rabbit that had died from a fixed virus hung by a thread attached to the cotton plug.

When a spinal cord had dried for the proper number of days, Viala cut it into small pieces with sterilized scissors. Then he put each piece into a small sterilized glass, added a few drops of veal broth, and pounded the mixture with a glass rod. The vaccine was covered and marked with a date. Each patient had his own row of these little dated glasses which contained a series of inoculations ranging in strength from a very weak vaccine to a very virulent one.

Several weeks after Pasteur publicly announced his rabies treatment, a ten-year-old girl was brought to him. Little Louise Pelletier had been slashed on the head by a mad dog which meant that the virus had only a short distance to travel to reach the brain. The wound was still festering. And she had been bitten thirty-seven days before!

Pasteur shook his head. “It is too late. I can do nothing,” he told her parents gently. But he could not resist their pleas and he agreed to treat Louise. When she died in spite of all his efforts, he felt as though he had lost one of his own children.

The death of Louise Pelletier was just what Pasteur’s enemies had been waiting for. As he had foreseen, they accused him of killing her, but Louise’s father did not join in their accusations. Years later he wrote to Pasteur’s son-in-law, Rene, “Among the great men whose lives I have been acquainted with, Pasteur seems to me the greatest of all. I know of no one else who would have done what he did for our little girl—sacrifice long years of work as a scientist, endanger a great reputation, and deliberately accept a painful failure, simply for the sake of humanity.”

The attacks did not prevent hopeful victims of mad dogs from arriving in increasing numbers, from foreign countries as well as the different parts of France. A New York newspaper asked for contributions to send four little American children who had been bitten by a rabid dog to Pasteur for treatment. When the children returned to New York, safe and well, a crowd of cheering citizens met their boat to give them a great welcome.

By March 1, 1886, Pasteur could report to the Academy of Sciences that a total of 350 people bitten by mad dogs had been treated at his clinic and only one of these had died—Louise Pelletier. In Pasteur’s report he urged the setting up of a special service for rabies vaccinations, since the flood of patients seeking treatment was growing much too large for his laboratory to handle.

Accordingly temporary quarters for a clinic were provided and the Academy of Sciences began plans for a permanent building to be called the Pasteur Institute. In addition to a large rabies treatment center, it would contain research laboratories and classrooms where physicians and scientists from other parts of France and foreign lands could learn how to establish antirabies clinics in their own communities.

March also brought him a new challenge with the arrival of nineteen Russians who had been terribly bitten by a rabid wolf. One man had had his upper lip and right cheek torn away by the great beast’s teeth. Some of the victims were so badly wounded they had to be carried to a hospital.

The bite of a mad wolf was known to be even more deadly than that of a dog; it was claimed that eighty-two out of every hundred victims would die. Two weeks had passed since the Russians had been bitten, a dangerously long period. Nevertheless Pasteur undertook to save them. He decided to speed up the inoculations, giving two each day to get the vaccine into their bodies as soon as possible.

Three of the Russians died but all the rest recovered. In gratitude the Czar sent his brother the Grand Duke Vladimir to Paris to bestow on Pasteur the Cross of the Order of Saint Anne, sparkling with diamonds. And the grand duke also brought a still more precious gift—a contribution of 100,000 francs for the proposed new institute that was to bear Pasteur’s name.

23

The Building of the Pasteur Institute

WHEN THE WORD spread that contributions were being sought to build a great Pasteur Institute in Paris, the response was overwhelming. Newspapers in foreign lands as well as in France began campaigns for funds. Rich people, poor peasants and workers, students and children sent in their offerings. So did the Czar of Russia, the Emperor of Brazil and the Sultan of Turkey. And when Pasteur read the list of contributors from Alsace, he found the name of his first patient, Joseph Meister.

A mammoth benefit performance was staged in Paris, with France’s greatest musicians, actors and other artists volunteering their services. Charles Gounod, the noted composer of Faust and other operas, conducted the orchestra as it played his famous Ave Maria.

After the benefit, a banquet was held for the performers and the committee planning the institute. Pasteur spoke, thanking them for donating their talents and for the pleasure they had given him. He added a little shyly, “Dare I confess that I was hearing most of you for the first time? I do not believe I have spent more than ten evenings in the theater in my whole life.”

Even while contributions were pouring in, the attacks against Pasteur did not cease. True, by this time most of the prominent physicians and scientists of France accepted the germ theory of disease. But to the few remaining defenders of the “old medicine” were now added a host of other critics who opposed Pasteur and his work for various reasons.

Some of these were horrified at the idea of injecting a virulent rabies virus into human beings; they believed it could kill patients with a disease they called “laboratory rabies.” Furthermore, they claimed, Pasteur’s treatment was useless because people bitten by mad dogs very seldom died of rabies. Pasteur was also a target for the antivivisectionists, who declared that animals should never be killed or caused pain in experiments—even when they were well cared for and their use resulted in discoveries that saved human lives.

On some occasions the public was invited to anti-Pasteur meetings, called to organize opposition to his work. He was accused of concealing his failures in order to improve his record. Certain newspapers went so far as to charge that his discoveries were a “hoax” and that he had lied in his scientific reports. Pasteur himself received hundreds of savage anonymous letters, and anonymous pamphlets denouncing him were distributed in the streets.

“I never knew I had so many enemies,” he said sadly.

As one means of answering his critics, he decided to run a complete list of the names and results for all the persons he had ever treated for rabies—failures as well as successes—in a new monthly publication called Annals of the Pasteur Institute. Actually, Pasteur had always been frank about reporting his failures and he had never claimed that his method would save every victim. He also agreed with those who said that many people bitten by mad dogs would probably escape rabies even without his vaccine. Nevertheless he had figures indicating that the vaccine was far from “useless.”

A report of the Paris health department, for example, showed that before his vaccine discovery, an average of sixteen persons died out of each hundred bitten by mad dogs. Another study of 320 persons bitten by rabid animals showed a death rate of forty per hundred. In contrast, Pasteur’s records showed a rate of about one death for each two hundred victims of rabid bites who had received his treatment.

The violent outbursts of criticism, the continual charges and counter charges took their toll on Pasteur’s health. He worried constantly that rabies victims who might be saved would now stay away from his treatment because of the scare stories. Nor could he help worrying about the health of the patients who were under his care.

His doctors, detecting new signs of heart trouble, advised him to get away from Paris. A rich patron of science, Raphael Bischoffsheim, offered Pasteur the use of a beautiful villa at Bordighera on the Italian Riviera. Pasteur accepted the invitation and in November he left Paris for the South, accompanied by his wife, their daughter and son-in-law, and two grandchildren.

The most savage and serious of the attacks on Pasteur came while he was in Italy. A child who had been treated in the Paris clinic died of rabies and his father charged that the boy had been killed by the treatment, not by the disease. Pasteur’s critics seized this opportunity to launch new accusations against him in the Academy of Medicine.

In Pasteur’s absence, his friends and collaborators in Paris fought the battle for him. They collected statistics indicating the success of his rabies treatment, and persuaded leading scientists to testify to his great skill and ability. They also had the dead child examined and made tests which showed that he had died from street rabies—that is, from the bite of a mad dog loose in the streets. The investigation proved that the boy could not possibly have died from the effects of the vaccination. Once again Pasteur and his laboratory won the support of the academy.

A bright spot in the midst of these latest attacks was the report of a commission appointed by the English government to study the antirabies vaccine. The Englishmen had spent fourteen months in a thorough investigation which included interviewing ninety persons whom Pasteur had treated. In July, 1887, this commission concluded: “It may therefore be considered as certain that Monsieur Pasteur has discovered a prophylactic method against hydrophobia which may be compared with that of vaccination against smallpox. It would be difficult to overestimate the utility of this discovery.” Pasteur’s treatment not only gave protection against rabies, they pointed out, but “similar means might be employed to protect man and domestic animals against other virus as active as that of hydrophobia.”

In November of the following year, the handsome new Pasteur Institute was dedicated by the President of the Republic. It soon became a busy place where rabies victims by the thousands sought treatment. The institute also developed into a leading center for research on virulent and contagious diseases. Pasteur’s pupils and followers, often called “Pasteurians,” were responsible for scores of important discoveries.

Emile Roux, his loyal assistant, later became a celebrated scientist in his own right. His research resulted in the development of a diphtheria antitoxin.

Elie Metchnikoff, a Russian who came to Paris to work with Pasteur, discovered the role of the white corpuscles in protecting the body against disease and eventually won a Nobel Prize for his research.

Alexander Yersin, another Russian scientist, collaborated with Roux on diphtheria research. Later in China, he discovered the microbe of bubonic plague and led the way to conquering it.

Albert Calmette, a French physician and bacteriologist, discovered a serum for treating snakebites.

Moreover, among the later employees at the institute were two men whose names Pasteur had made famous. Joseph Meister became the concierge of one of the buildings. Jupille, his second rabies patient, worked in a laboratory there.

New Pasteur Institutes were soon springing up in other cities of Europe and on far-off continents. These helped to perpetuate Pasteur’s influence throughout the world.

With the opening of the institute in Paris, the Pasteurs moved from their old home at the Ecole Normale to a comfortable apartment that had been prepared for them in the new building. They still lived simply and unpretentiously, much as they had thirty years earlier when Louis became the new director of scientific studies at the Ecole and was just beginning his fermentation studies.

Statue of Fupille struggling with the mad dog, on the grounds of the Pasteur Institute. It honors the bravery of the young shepherd who saved his companions from the dog's attach and became Pasteur s second patient for the anti-rabies vaccine.

Pasteur was now no longer able to carry on research; he had suffered another attack of paralysis and his health was poor. But he liked to visit the laboratories of the institute and keep track of the work in progress.

Every morning he would go to the rabies clinic before the patients arrived. He kept a sharp eye on the preparation of the vaccine and watched as the doctor gave each patient an injection. As the needle entered the skin he would wince—just as he had done twenty years before when Roux was collecting samples for him from patients in the hospitals.

It was also Pasteur’s habit to question the rabies victims about themselves. When they were poor and friendless he saw that they got money and other help. He was especially gentle with children who were badly bitten or frightened by the injections. Comforting them and drying their tears, he would give them bright new coins which he kept on hand for just that purpose.

On December 27, 1892, the great Jubilee celebration was held in honor of Pasteur’s seventieth birthday. Plans for it had been started six months before by scientists in Denmark, Sweden, and Norway—then France and other countries joined in the preparations.

The vast hall of the Sorbonne was packed with delegates from French and foreign scientific societies, professors, and hundreds of students. On the stage were seated ambassadors, high public officials, and the presidents of the French Senate and Chamber. Five delegates in splendid uniforms represented the five famous academies that made up the French Institute.

As the band played a triumphal march, Louis Pasteur entered and the great audience rose to greet him. Leaning on the arm of the President of the Republic, he walked very slowly to the center of the stage.

In addition to Sir Joseph Lister and other renowned visitors from abroad, the speakers included the Minister of Public Education and the president of the students’ organization. Even the life secretary of the Academy of Medicine, the scene of so many of Pasteur’s stormiest battles, offered the tribute of his organization.

Since Pasteur’s voice was too weak from illness to be heard by the crowd, his reply had to be read by his son. The great scientist thanked the French and foreign delegates for their tributes, then he gave a special message to the students.

“Young men,” he counseled them, “say to yourselves first: ‘What have I done for my education?’ and as you advance, ‘What have I done for my country?’ until the time comes when you have the great happiness of knowing that you have contributed in some way to the progress and to the good of mankind.”

This seventieth birthday celebration was Pasteur’s last appearance before the public. His days were now spent quietly. He continued to enjoy visits with his friends and former students, his children, and especially his two grandchildren. One of his favorite visitors was Charles Chappuis, his friend for fifty years and now honorary rector of the Academy of Dijon. With Chappuis and his other friends, Pasteur particularly liked to talk about his crystal experiments. Crystals had never lost their fascination for him and he regretted that because of all his other research he had been forced to give up his explorations into their mysteries.

In November of 1894 he had a third severe stroke and although he made a partial recovery, he remained an invalid. When the hot summer came, Pasteur asked to be taken to stay in his old room at Villeneuve l’Etang, just outside Paris. The dogs and rabbits he had needed for his rabies research were gone now. Instead, the stables were filled with horses used by Roux in the preparation of diphtheria antitoxin.

The afternoons Pasteur spent sitting under the pines and beech trees while Madame Pasteur or Marie Louise read to him and his grandchildren played on the grass. But his paralysis was gradually increasing and it became more and more difficult for him to move and speak.

By the last week of September he was too weak to leave his bed. And it was on September 28, 1895, that he died very peacefully in his room at Villeneuve I’Etang, with his family and a group of his Pasteurians around him.

France arranged an impressive state funeral for her famous son. A beautiful marble chapel was built at the Pasteur Institute and here he was buried.

Today, in the busy laboratories above the chapel, researchers are still making new discoveries along the trails that Louis Pasteur pioneered in the science of microbiology.

Index

Academy of Sciences

Acetic acid fermentation

Aerobic bacteria

Alcohol amyl fermentation

Anaerobic bacteria

Annals of the Pasteur Institute

Anthrax

Asymmetrical crystals

Attenuated culture

Autoclave

Bacilli, Bacteria

Balard, Antoine Jerome, chemist

Barbet, Monsieur, schoolmaster

Barbier, Captain Barruel, Dumas’ assistant

Bastian, Dr. Henry Charlton, physician

Beer Beet juice

Bertin, Pierre Augustin, physicist

Besangon school

Bigo, Monsieur, alcohol manufacturer

Biot, Jean Baptiste, scientist

Bismarck, Otto von, German chancellor

Bouillon. See Nutrient bouillon

Bourrel, veterinary surgeon

Boutet, veterinarian

Buchner, Eduard, chemist

Budding

Butyric acid

Calmette, Albert, Pasteurian bacteriologist

Carbon dioxide

Catalyst,

Chamberland, Charles Edouard, Pasteur’s assistant

Chappuis, Charles, Pasteur’s friend

Chicken cholera

Childbirth fever

Cocci

Colin, G., veterinary professor

Compound, chemical

Contagious disease

Crystals and crystallography

Pasteur’s work in

Culture  Culture medium

Cycle of life

Czar of Russia

Davaine, Dr. Casimir Joseph, physician

Delafosse, Gabriel, professor of mineralogy

Dimorphism, Pasteur’s research on

Dubos, Dr. Rene J., scientist

Duclaux, Emile, Pasteur’s assistant

Dumas, J. B., chemist

Ecole Normale

Element, in chemistry

Enzymes

Epidemic

Etiology

Fabre, Jean Henri, writer on insects

Facets

Ferment see also Fermentation

Flacherie

Flasks

Franco-Prussian War

French Academy

Germ

Germ theory of disease

Goniometer

Gounod, Charles, composer of music

Grancher, Jacques Joseph, Pasteur’s assistant

Guérin, Dr. Alphonse, surgeon

Guérin, Jules, surgeon

Haiiy, Rene Just, authority on crystals

Herschel, John, scientist

Hervieux, Dr., physician

Huxley, Thomas Henry, biologist

Hydrophobia

Immunity

Incubation of disease

Incubator

Infectious disease

Injection

Inoculation  see also Vaccines and vaccination

Jaillard, French scientist

Jenner, Edward, physician

Joly, Nicholas, aide to Felix Pouchet

Jubilee celebration for Pasteur

Jupille, Jean Baptiste, hero and rabies victim

Kestner, discoverer of paratartaric acid

Koch, Dr. Robert, scientist

Lactic acid fermentation

Laurent, Marie. See Pasteur, Marie

Leeuwenhoek, Antony van, scientist

Leplat, French scientist

Liebig, Justus von, chemist,

Light waves

Lister, Sir Joseph, surgeon

Littre, Emile, philosopher and dictionary editor

Living matter, Pasteur’s theory of

Loir, Adrien, Pasteur’s nephew and assistant

Louis Philippe, King of France

Medium. See Culture medium

Meister, Joseph, rabies victim

Metchnikoff, Elie, Pasteurian and Nobel Prize winner

Microbes and microbiology , see also Microorganisms

Microorganisms

in wine yeasts and molds

Milk, fermentation of

Mitscherlich, Eilhard, chemist

Mold

Molecular asymmetry

Musset, Charles, aide to Felix Pouchet

Mycoderma aceti

Napoleon III

Nutrient bouillon

Onimus, Dr., member of Academy of Medicine

Optical activity

Osteomyelitis

Oxygen

and microbes

and winemaking

Paratartaric acid, see also Racemic acid; Tartrates

Paris Pharmaceutical Society

Pasteur, Camille, daughter of Pasteur,

Pasteur, Cecile, daughter of Pasteur

Pasteur, Claude Etienne, grandfather of Pasteur

Pasteur, Jean Baptiste, son of Pasteur

Pasteur, Jean Joseph, father of Pasteur

Pasteur, Jeanne, daughter of Pasteur

Pasteur, Louis

summary of his work

birth

childhood,

student at Barbet and Besan on schools

student at Ecole Normale

crystallography research

in National Guard

mother’s death

teacher at Dijon

professor at Strasbourg

personal appearance

marriage

children

racemic acid research

chevalier of Legion of Honor

professor at Lille

fermentation studies

administrator at Ecole Normale

awarded Rumford Medal

spontaneous generation research

study of anaerobic microorganisms

vinegar research

member of Academy of Sciences

wine research

silkworm disease research

awarded degree by University of Bonn

suffers cerebral hemorrhage

searches for son

beer research

elected to Academy of Medicine

studies of germ theory of disease

advocates sterilization

receives pension from government

conquest of anthrax

study of childbirth fever

study of chicken cholera

grandchildren

challenged to duel

rabies research

awarded Grand Cross

at International Congress of Medicine

elected to French Academy

research on swine fever

awarded Cross of the Order of Saint Anne

Pasteur Institute

seventieth birthday celebration

death,

Pasteur, Marie, wife of Pasteur

Pasteur, Marie Louise, daughter of Pasteur

Pasteur Institute

Pasteurians

Pasteurization of beer milk wine

Pébrine

Pedro II, emperor of Brazil

Pelletier, Louise, rabies victim

Pneumonia Polarimeter

Pouchet, Felix Archimede, naturalist

Prince Imperial of France, son of Napoleon III

Protozoa

Provostaye, Frederic de la, crystallographer

Pure culture

Putrefaction

Quartz crystals,

Rabies

Racemic acid

Revolution of

Rossignol, editor of Veterinary Press

Roux, Emile, Pasteur’s assistant

Royal Society of London

Sedillot, Dr. Charles Emmanuel, surgeon

Septic vibrio

Septicemia

Silkworms, title page of Pasteur’s book on

Smallpox

Spontaneous generation

Spores

Staphylococcus

Stereochemistry

Sterilization

Streptococcus

Swine fever

Symmetrical crystals

Symptom

Tanning

Tartrates and tartaric acid

Thuillier, Louis, Pasteur’s assistant

Toussaint, H., veterinarian

Trepanning

Tyndall, John, physicist

Vaccines and vaccination

anthrax

chicken cholera

rabies

smallpox

Vallery-Radot, Rene, Pasteur’s son-in-law

Vercel, Jules, Pasteur’s friend

Viala, Eugene, Pasteur’s assistant

Villa, Vicentina

Vinegar

Virulent diseases

Virus

Vulpian, Alfred, physiologist

Wine

microorganisms in

pasteurization of

Yeast

Yersin, Alexander, Pasteur Institute scientist,

ABOUT THE AUTHOR

MARY JUNE BURTON is a free-lance writer on science and industrial subjects. She has been Managing Editor of Tomorrow’s Scientists, student publication of National Science Teacher’s Association, and an editor of American Education Publications. She is a native of Springfield, Ohio, and a graduate of Antioch College. She lives in New York City.

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