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 amcebse 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 



