HISTOR Y OF RESEARCH ON TUBERCLE. 207 



bacillus was made by Koch in March 1882, and a full 

 account of his researches appeared in 1884 (Mitth. a. d. 

 k. Gsndhtsamte, Berlin). Koch's work on this subject will 

 remain as a classical master-piece of bacteriological research, 

 both on account of the great difficulties which he success- 

 fully overcame and the completeness with which he demon- 

 strated the relations of the organism to the disease. The 

 two chief difficulties were, first, the demonstration of the 

 bacilli in the tissues, and, secondly, the cultivation of the 

 organism outside the body. For, with regard to the first, 

 the tubercle bacillus cannot be demonstrated by a simple 

 watery solution of a basic aniline dye, and it was only after 

 prolonged staining for twenty-four hours with a solution of 

 methylene-blue with caustic potash added, that he was able 

 to reveal the presence of the organism. Then, in the 

 second place, all attempts to cultivate it on the ordinary 

 media failed, and he only succeeded in obtaining growth on 

 solidified blood serum, the method of preparing which he 

 himself devised, inoculations being made on this medium 

 from the organs of animals artificially rendered tubercular. 

 The fact that growth did not appear till the tenth day at 

 the earliest, might easily have led to the hasty conclusion 

 that no growth took place. All difficulties were, however, 

 successfully overcome. He cultivated the organism by the 

 above method from a great variety of sources, and by a 

 large series of inoculation experiments on various animals, 

 performed by different methods, he conclusively proved 

 that the bacilli from these different sources produced the 

 same tubercular lesions and were really of the same nature. 

 His work was the means of showing conclusively that such 

 conditions as lupus, " white swelling " of joints, scrofulous 

 disease of glands, etc., are really tubercular in nature. 



Tuberculosis in Animals. Tuberculosis is not only the 

 most widely spread of all diseases affecting the human 

 subject, and produces a mortality greater than any other, 

 but there is probably no other disease which affects the 

 domestic animals so widely. We need not here describe in 

 detail the various tubercular lesions in the human subject, 



