Louis Pasteur Proves Germs Cause Disease
It was a beautiful day in May. A great day to be alive. I am standing here in the middle of a field in the small village of Pouily le Fort, just a few miles south of Paris, France. I'm thinking about an event that happened in this field just a little over one hundred years ago. I'm thinking that if it hadn't been for that event (and some others like it about that same time) I might not be here to think what a beautiful day in May this is. Because I would not be alive. Nor would you. Here is what happened on ... June 2, 1881.
A learge crowd of doctors, government inspectors, veterinarians, farmers, reporters, and public curiosity seekers came by train from Paris to this small town. They were hoping to see a miracle and they were not disappointed. On the callenge of a local veterinarian, the famous chemist Louis Pasteur was about to demonstrate his radical new theory ... that it was germs that cause disease. He would show the world a radical new practice...a way to kill germs and to prevent disease. Here is how he did it.
In early May, Pasteur and his assistants came to this village farm to inject twenty four sheep, six cows, and one goat with a weakened anthrax bacteria. A control group of equal numbers was left without injections. A few weeks later they came again and injected the first group of animals with another dose of weakened anthrax bacteria. In a third visit, just a few days before June 2, all forty eight sheep, twelve cows and two goats were given lethal injections of the deadly anthrax bacteria.
Now, on June 2, with all present and eagerly holding their breath, Pasteur proudly let out into this field all twenty four sheep, six cows and onc goat that he had injected earlier with his new vaccine. All of these vaccinated animals were in fine health, with nary a sniffle.
Then he led the crowd to another part of the field where twenty one of the control group, the non-vaccinated sheep and the goat, were dead. Two more sheep died as the onlookers watched and the last non-vaccinated survivor died before the end of the day.
The demonstration was a dramatic success. The new theory worked! He had proved that anthrax was caused by germs. And he had proved that he could keep those germs-anthrax bacteria-from causing the disease! In olher words, after thousands of years of human failures, one man, Louis Pasteur, had found a way to give doctors tools of genuine help to animals, and to human beings, when they were sick. He had found a key to make medicine a science as well as an art.
You see, make no mistake about it, for thousands of years before Pasteur, medicine was not a science. For thousands of years beforr Pasteur, doctors were helpless in the face of disease. (Many times it was worse than that. Doctors carried disease, and made people sicker rather than healthier.) Tne result: millions upon millions of human beings died early deaths from killers like smallpox, malaria, diphtheria, cholera, tuberculosis, bubonic plague. Because of these early deaths, throughout all human history the average life span of human beings never rose much above the age of 30 years. Indeed, a few people lived into old age, but MOST people died in infancy or in childhood from one of these dreadful infectious diseases!
Today, by contrast-mainly because of the knowledge given to us by scientists like Pasteur, few people die in infancy or childhood and most people around the world live to be over 70 years.
How did such a giant step fonvard happen?
Pasteur was the most justly famous and without doubt the most productive of the new scientific wizards responsible for this advance. But he was not alone.
One of the most important of his contemporaries (and fierce competitors) was the German dodor and bacteriologist, Robert Koch. It was Koch who first isolated anthrax bacteria. Koch is also given credit for developing crucial techniques for identifying and then growing germs in the laboratory in pure cultures. Besides isolating and growing the bactenia that caused anthrax, Koch was also the one who discovered the cause of many other germ-caused diseases including the two worst killers of the 19th century, cholera and tuberculosis.
These giant steps of Pasteu, Koch and the other microbe hunters of the late nineteenth century were built, like all scientific triumphs, on the work of many other scientists and technicians who came before. Let's take note of just two of the most important.
One. In the case of scientific medicine, we could not conquer germ-caused diseases until we knew there were such things as germs. This world of microscopically small germs was totally unknown to human beings everywhere until an eccentric town janitor in Holland-Anton von Leuwenhoek-perfected some of the first microscopes! This happened a hundred and fifty years before Pasteur and Koch.
While more well-known world explorers were describing their adventures in the new worlds of America, Asia and the South Pacific, Leewenhoek explored his new world of smallness with the help of his new microscopes and found things that no one had ever seen before.
He called the inhabitants of his new world, "little beasties." He found them everywhere he looked ... in rain water, in food, in dust, in air,... in his own mouth and blood. He saw them, drew pictures of them, described them in detail in hundreds of letters to scientists in Great Britain. He did not know that scientists to come would show that though most of his "little beasties" were harmless to human beings and many were important links in the web of life on earth, a few of them would turn out to be the mosf powerful and ruthless of all killers to ever stalk the earth.
Leeuwenhoek lived and worked in the late 17th and early 18th century, about the time our country was becoming settled but was still a colony of Great Britain. Around the time of the American revolution in 1776 a second breakthrough happened to help prepare the way for the scientific medicine of our own 20th century. This one happened here in the dairy country of southwestern England.
Smallpox was an especially dreaded disease in those days. It was so common a disease in Europe and America that few people escaped having pock-marked face. They were the lucky ones. Many people who caught smallpox died. A country doctor, Edward Jenner, noticed that milkmaids who got a similar but much milder disease, cowpox, never seemed to get smallpox. Operating on a hunch (and taking a big chance), he injected himself and a few others with material from cowpox sores and found that this injection gave immunity to the dreaded smallpox.
This discovery made Jenner a great celebrity. People in England, Europe and America clamored to get vaccinations. No one knew yet that the actual cause of smallpox was a virus, but the basic technology of immunization had been discovered and given an early and successful trial. This vaccination model said, inoculate the person with a small amount of a toxic substance. This inoculation will stimulate the human body itself to produce chemicals called antitoxins. These antitoxins will Eight and neutralize the "poisons" causing the disease. In this way the body will develop immunity to future doses of the same or similar toxic substances.
Jenner had no way of knowing about the "germs" that caused smallpox because they could not be seen with the microscopes of his day. In the early 19th century the compound microscope was invented and improved. This compound microscope had two or more lenses and could magnify much more than Leeuwenhoek's single lens microscopes. Now it was possible to see and to identify disease-causing bacteria and viruses.
By the mid 19th century chemistry, too, was making rapid progress and the new sciences of biochemistry and microbiology were born. And now we come back to Louis Pasteur. Nowhere were discoveries in these new fields more frequent or more important than in laboratories of the chemist Louis Pasteur in Paris, Strassburg and here in his ancestral home in Arbois.
In fact, it was right here in Arbois that the young chemist made his first important biological discovery. It was a discovery in a seemingly unrelated field, but one that was to lay the groundwork for his all-important germ theory of disease a few decades later.
The French had been making wine for centuries. Winemaking was an art and craft. Like so many arts and crafts the people who did them knew how to make wine alright but they didn't know why it worked the way it did. In 1856 there was a crises in the French wine country. For unknown reasons much of the wine was turning sour even though the wine makers were using the time-tested recipes.
Pasteur didn't know anything about wine making but he put his microscope and his knowledge of chemistry to work. He turned his microscope on the wine vats. He first found out the secret of just how wine was made from grape juice. People already knew there were things called yeasts in the fermenting grape juice. What they didn't know was that these yeasts were actually living organisms-"little beasties" as Leeuwenhoek wouldhave called them-and it was these living organisms that were responsible for turning sugar into alcohol, for making wine from grape juice!
Where did the yeasts come from?
By carefully growing grapes in the open air and comparing them with grapes grown shielded from the open air, he found that only the grapes grown in the open air had yeasts on their skins. The yeasts must have come out of the air itself. When the grapes are harvested, the yeasts come along. They multiply in the wine barrels and using the sugar of the grape juice they ferment the juice, making it into wine! Later he found a similar thing happened with grains used to make beer.
When he put his microscope to the vats containing the spoiled wine he found that in addition to the living wine yeasts they had other living germs that the good wine did not have. It was these spoiling bacteria that made the wine sour! How to cure it? How to get rid of the bad bacteria but keep the good yeasts?
Pasteur began experimenting and finally found that gently heating the grape juice to 55 degrees centigrade would kill the spoiling bacteria but not harm the wine. This process of gentle heating was given the name pasteurization and it saved the French wine industry. Later it was also adapted to beer making, to milk production, to juice preservation and to many other food preservation technologies.
An interesting aside. Pasteur had a family to support and he was not a wealthy man. Nonetheless, even though he took out a patent on his pasteurization process, and took a major part in designing the industrial equipment to do it, he released the patent to the public and never profited financially from this historic life-saving invention.
Pasteur moved from saving the wine industry to doing the same thing for the beer industry in France, and then the silk industry, where (after three years of hard work, including many failures) he found a way to prevent a silkworm disease, also using his new microbial techniques.
Slowly it dawned on Fasteur that if diseases of plants and animals were caused by germs, the same thing must be true for human beings! Germs hurt and killed people in the same way germs ruined wine and beer, and killed silkworms. This idea changed our world!
In the last half of his life Louis Pasteur used the same techniques to save animals from anthrax and to save human beings from rabies. Important as these specific achievements of Pasteur were, away and by far the most important pay off from his work was that germ theory of disease itself! It was this theory that led to such remarkable progress in the late 19th century and now in our 20th century. Using the germ theory of disease scientists finally conquered, one by one, dreaded killers like diphtheria, malaria, childbed fever, tuberculosis, cholera and polio.
I say "conquered." Let's get a little perspective on that. In 1882 (the year after Pasteur demonstrated his success with anthrax) the German bacteriologist Robert Koch pointed out in a speech to a Berlin audience just how deadly the germ caused tuberculosis was.
"Even the most dreaded infectious diseases, such a bubonic plague, asiatic cholera, etc. must rank far behind tuberculosis," said Koch. "Statistics teach that one-seventh of all human beings die of tuberculosis, and that if one considers only the productive middle age group, tuberculosis canies away one-third and often more of these."
"Conquered" means that today instead of one out of three young people dying of tuberculosis, perhaps one out of a million die of tuberculosis.
The germs that cause tuberculosis and malaria and cholera and polio still exist on earth. And some of these germs are themselves changing into new varieties that require newly designed drugs and vaccines to combat them. But thanks to the work of Pasteur and his fellow microbe hunters of the 19th century we know how to do this today.
Today there are some germ-caused diseases we have no effective weapons to combat. AIDS for instance. Right now, in the final decade of the 20th century scientists are working desperately-using the very same basic techniques pioneered by Pasteur-to find ways of stopping this AIDS virus.
I said at the beginning of this program that if it had not been for the work of Louis Pasteur (and other microbe fighters of the late 19th century) I would most likely not be living today. Nor would most of you. It is exciting and it is sobering to look back at human history and read now of the great events and the great tragedies. One of these tragedies is that the greatest, most historically significant events were not reported at all at the time they happened. If you had been living in 1881, for example, the year Pasteur demonstrated his triumph over anthrax, you would not have seen it reported at all in the popular press of the United States. By far the biggest story of that year was the assassination of our president, James Garfield. (On a personal level, I recently found out that it was in that same year two of my great aunts and uncles died of cholera on the same day in Toledo, Ohio.)
Louis Pasteur lived to the age of 75 and worked right up to the end of his life even though half paralyzed from a stroke at the age of 50. When he was honored by the French Republic on his seventieth birthday in the great amphitheater of the Sorbonne, his words of thanks are as relevant today as they were in 1888.
"Delegates from foreign nations," he addressed the audience,"you bring me the deepest joy that can be felt by a man whose invincible belief is, that Science and Peace will triumph over Ignorance and War, that nations will unite, not to destroy, but to build, and that the future will belong to those who will have done most for suffering humanity."
Turning to the young students in the audience he added, "Have faith in those powerful and safe methods, of which we do not yet know all the secrets. And, whatever your career may be, do not let yourselves be discouraged by the Sadness of certain hours which pass over nations. Live in the serene peace of laboratories and libraries."