500 Tuberculosis. 



toneal injection of tuberculous sputum. Bollinger obtained tbe same 

 result by the injection of tuberculous lung tissue. 



As the result of a statistical study of the various feeding experi- 

 ments with the transmission of tuberculosis, Cohnheini declared in 1879 

 that the correct diagnosis of tuberculosis could no longer be made from 

 a purely anatomical point of view and that the etiological viewpoint 

 alone was justifiable. He maintained further that the cellular structure 

 of the nodules was as little characteristic of a purely tuberculous pro- 

 cess as the tendency to cheesy degeneration which had been emphasized 

 by Laennec. He held that either process could be considered as tu])er- 

 culous only when their infectious nature had been demonstrated. Fur- 

 ther, since other tubercles or cheesy products are not infectious, though 

 similar in their anatomical structure, the infectiousness of the inie 

 tubercle uuist be due to a specific virus. 



Nothing now was lacking in the chain of evidence but the recogni- 

 tion of this specific virus in order that the infectious nature of tuber- 

 culosis might be recognized as a scientifically demonstrated fact. This 

 was accomplished by Robert Koch in 1882 when he proved by incon- 

 trovertible evidence that tuberculosis in man as well as tuberculosis in 

 animals was dependent upon the pathogenic action of a morphologically 

 and culturally characteristic bacterium. The theory of the infectious- 

 ness of tul)erculosis was hereby placed upon a firm foundation and fur- 

 ther research was thenceforth directed to the establishment of the vari- 

 ous conditions under which infection took place and the means by which 

 the discovery of efficient methods of prevention was possible. 



In recent years the study of the etiology of tuberculosis received 

 a new stimulus when Koch, in an address before the Tuberculosis Con- 

 gress of London in 1901, declared that bovine and human tuberculosis 

 were different diseases, that the human disease was not transmissible to 

 cattle and that it was not necessary to observe special precautions to 

 protect man against pearl disease or bovine tuberculosis. This opinion 

 was diametrically opposed to former views expressed by him or held by 

 the medical profession in general. The various commissions which 

 were thereupon appointed by the German government as well as the 

 English Royal Commission for the study of this question did not 

 express an unqualified endorsement of the views expressed by Koch. 

 Nevertheless they produced valuable information regarding the mor- 

 phological, cultural and pathogenic characteristics of tubercle bacilli 

 of different origin. Simultaneously the question of the exact mode 

 of infection was again forced into the foreground of investigation. At 

 this time two theories, sharply opposed one to the other, received general 

 recognition, viz., the view of Fliigge who held that infection occurred 

 chiefly through inhalation of the virus into the air passages, and that of 

 Calmette who held that infection by way of the alimentary canal was of 

 most frequent occurrence. In recent years, however, the tendency is to 

 accept a combination of these two views on the modes of infection, while 

 the importance of either mode is recognized. 



These as well as the extraordinarily numerous and painstaking 

 investigations of other details of the tuberculosis question, the numerous 

 associations, congresses and conferences which were organized in rapid 

 succession, and the active social and economic interest which developed 

 with reference to this question, give cause to hope for a gradual repres- 

 sion of this devastating disease. As far as tuberculosis of man is con- 

 cerned the various public sanatoria and dispensaries have produced 

 happy results in the way of disseminating popular knowledge concern- 

 ing the disease. The results of a similar campaign for the suppression 



