ROBERT KOCH. 655 
body. Miliary tubercles were examined microscopically for some 
signs of a microbe, but for long without success. At last, by a modi- 
fication in the method of staining, a fine bacillus was discovered, and 
its presence in the majority of preparations established. Efforts to 
grow the organism in pure culture at first failed, but subsequently, 
by infinite patience, he succeeded in growing it upon coagulated 
serum. Once isolated and grown upon a succession of media, the 
establishment of the bacillus as the etiological factor presented no 
difficulty, and at the Physiological Society in Berlin on March 24, 
1882, Koch presented the proof that he had discovered the cause of 
one of the most widespread and dreaded of human diseases. 
From the discovery of the cause of a disease, its prevention or cure 
does not necessarily follow, but in the campaign against an enemy it 
is of first importance to be acquainted with his nature and peculiari- 
ties. Koch interested himself, at once, in studying the life history 
and methods of warfare of the tubercle bacillus. These studies were, 
however, interrupted. Cholera was in Egypt and threatened Europe, 
and the German Government organized a commission, with Koch as 
leader, to proceed to Egypt to study the disease, and draw up recom- 
mendations for dealing with it, should it reach Germany. Shortly 
after reaching Egypt the outbreak there ceased. In the meantime, 
however, Koch had obtained important information leading him to 
suspect a particular comma-shaped bacillus as the specific cause of 
the disease. The material for the furtherance of his inquiry having 
failed in Egypt, Koch proceeded to India, where cholera is endemic, 
and completed his investigations. He satisfied himself that the 
comma bacillus was the constant companion of the cholera disease, 
that its abundance was commensurate with the severity of the 
attack, and that it penetrated beneath the epithelium in the affected 
part. He never succeeded in obtaining it from the healthy or dis- 
eased intestine, other than in the case of cholera. It was com- 
paratively easy to obtain it in pure culture, and its characteristics 
were studied, but the completion of the evidence to convict this 
organism was lacking, as a true cholera process can not be artificially 
produced in any of the laboratory animals. Incidentally, whilst in 
Egypt, he discovered amcebe in dysentery, and the bacillus responsi- 
ble for the widespread ophthalmia in that country. 
As previously mentioned, at the time Koch was ordered to Egypt 
to investigate cholera he was engaged in the attempt to discover 
some means to modify the infection by the tubercle bacillus in the 
animal body. Proceeding on the assumption that the tubercle 
bacillus exercises its pathogenic effects by means of a chemical poison, 
Koch investigated the action of the dead bacilli and their products 
upon normal animals, and also the effect of a previous injection with 
dead bacilli upon a subsequent inoculation of living ones. This 
