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The story of Pasteur, Koch and the tiny enemies of mankind - Germs.

Dr Sampurna Roy MD                


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"In the field of observation, chance favours only the prepared mind." -Louis Pasteur


The most dangerous enemies of mankind are so tiny that they can be seen only with microscope.

Some are so minute that they cannot be seen at all, but are known from the disease and the effects that they bring about. These tiny one-celled organisms are the germs or microbes.

From the study of these organisms has come one of the greatest achievements in human history, the discovery of why and how diseases begin and how they can be prevented or cured.

For thousands of years people had no idea of the existence of germs and made all kinds of wild guesses at the reasons why they became ill and sometimes died from their illnesses. Some thought that each disease was caused by an evil spirit inside the patient's body, and they tried to coax the spirit out by songs or drive it away by some terrible spurious medicines. This was one of the jobs of the witch doctors or medicine men, who are still found today among primitive tribes in remote areas. Another strange idea was that diseases were caused by poisonous gases from stagnant water or decaying bodies and the sickness passed from one victim to another in waves, like the waves in water.

In the second half of the 19th century the existence of germs was made quite clear. The two men mainly responsible for making it obvious were Louis Pasteur, a Frenchman, and Robert Koch, a German.

In 1865 the french silk industry was threatened by a disease called pebrine which attacked silkworms. Pasteur was asked to study this disease and find what was causing it. He discovered that it was due to tiny bodies which were living on the worms, and he was able to work out a cure for the disease.

In his work on pebrine, Pasteur first stated the theory that disease is caused by germs. He continued his work on germs until his death in 1895.

Robert Koch was born in Germany in 1843. He was a surgeon in the Franco-Prussian War (1870-1871) and later became a country doctor. All the time that he could spare from attending to his patients was spent with his microscope.

He made a special study of anthrax a serious disease which affects both men and animals, and in 1876 proved for the first time that anthrax is caused by a germ.

He also found a method of staining germs with dyes so that they could be more easily seen and studied under microscope.

In 1882 he announced the greatest of his discoveries, that of the germ which causes tuberculosis, and after a visit to Egypt and India he was able to trace the cholera germ.

Koch travelled all over the world studying outbreaks of disease. He studied sleeping sickness and rinderpest (an infectious disease of cattle) in South Africa, bubonic plague in India and malaria in Java and Ceylon. The Nobel Prize for medicine was awarded to him and he received many other honours before his death in 1910.

Every infectious disease is caused by a particular kind of germ and by no other kind. For example - The microbe that causes scarlet fever, for example, cannot cause diphtheria. Neither can diptheria be caused by anything but its own microbe. This great discovery of the connection between microbes and disease brought about the germ theory of disease which has taken the place of all the old theories.

The general name germ was used for all these harmful organisms, as germ also means a seed, and the germ is the "seed" of its disease.

Later the names microbe and microorganism, which both mean "tiny living thing", became used commonly used.

As researchers learned about germs they found that the tiny, one-celled organisms might be animals or members of the vegetable kingdom. So new names were used to describe them. The animals forms are protozoa and the vegetable forms are bacteria. A third group of germs, which are called viruses was described later.

Nowadays it is possible to prevent a person from catching a serious infectious disease by giving him what is known as " artificial immunity" to that  disease. Various infectious diseases are prevented by vaccination.

The word vaccination comes from vacca, the Latin for cow. Vaccination, which proved to be the the best method of preventing smallpox was discovered by Dr Edward Jenner in 1796.


"If my efforts have led to greater success than usual, this is due, I believe, to the fact that during my wanderings in the field of medicine, I have strayed onto paths where the gold was still lying by the wayside. It takes a little luck to be able to distinguish gold from dross, but that is all." -  Robert Koch

For more information on various infectious diseases visit - Infectious Disease Online


Further reading:

The Legacy of Robert Koch:  

The Germ Theory of Disease

An Address on Cholera and its Bacillus

Remarks on Trypanosome Diseases

A Further Communication on a Remedy for Tuberculosis


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Dr  Sampurna Roy  MD

Consultant Histopathologist (Kolkata - India)







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