The Germ Theory of Disease

The necessary theory came with Pasteur, whose interest in microorganisms dated from his concern with the fermentation problem. This interest now led to something more.

In 1865, the silk industry in southern France was being dealt a staggering blow by a disease that was killing the silkworms, so the call went out once more for Pasteur. He used his microscope and found a tiny parasite infesting the sick silkworms and the mulberry leaves that were being fed to them. Pasteur's solution was drastic but rational. All infested worms and infected food must be destroyed. A new beginning must be made with healthy worms and clean food. This worked and the silk industry was saved.

But to Pasteur it seemed that what was true of one infectious disease might be true of others. A disease could be caused by microorganisms. It could then be spread by coughing, sneezing, or kissing, through wastes, through contaminated food or water. In each case, the disease-causing microorganism would spread from the sick man to the healthy one. The physician in particular, thanks to his necessary contact with the sick, might be a prime agent of infection.

The last conclusion had indeed been reached by a Hungarian physician, Ignaz Philipp Semmelweiss (1818-65). Without knowledge of Pasteur's theory, he nevertheless could not help but notice that the death rate from childbed fever among women in Vienna hospitals was dreadfully high, while among women who gave birth at home with the help of ignorant midwives it was quite low. It seemed to Semmelweiss that doctors who went from the dissecting room to the operating room must be carrying the disease somehow. He insisted that doctors wash their hands thoroughly before approaching the woman in labor. Whenever he could carry that through, the death rate fell. The offended doctors forced him out, however, and the death rate rose again. Semmelweiss died defeated and just too soon to see victory. (In the United States, at about the same time, the American physician and poet, Oliver Wendell Holmes (1809-94), carried on a similar campaign against the dirty hands of obstetricians, and won considerable abuse for himself.)

Once Pasteur advanced his "germ theory of disease”, however, conditions slowly changed. There was now a reason to wash, and however much conservative physicians might protest against the new-fangled notion, they were slowly forced into line. During the Franco-Prussian War, Pasteur managed to force doctors to boil their instruments before using them on wounded soldiers and to steam their bandages.

Meanwhile, in England, a surgeon, Joseph Lister (1827-1912), was doing his best to reform surgery. He was putting "anesthesia" into use, for instance. In this technique, a patient breathed a mixture of ether and air. This caused him to fall asleep and become insensible to pain. Teeth could be extracted, and operations performed, without torture. Several men had contributed to his discovery but the lion's share of the credit is usually given to an American dentist, William Thomas Green Morton (1819-68), who arranged to have a facial tumor removed from a patient under ether in the Massachusetts General Hospital in October 1846. This successful display of anesthesia quickly established it as part of surgical procedure.

However, Lister was distressed to find that even though an operation might be painless and successful, the patient might still die of the subsequent infection. When he heard of Pasteur's theory, the thought occurred to him that if the wound or surgical incision were sterilized, infection would not catch hold. He began by using carbolic acid (phenol) and found it worked. Lister had introduced "antiseptic surgery."

Gradually, less irritating and more effective chemicals were found for the purpose. Surgeons took to wearing sterilized rubber gloves and face masks. Surgery was finally made safe for mankind. If Pasteur's germ theory had done this alone, it might have been enough to make it the most important single discovery in the history of medicine. However, it accomplished more, much more, and its unparalleled importance cannot be challenged.