Transmission of Bovine Tuberculosis. 105 



were tenaciously retained. In one of the cases the bacillus persisted in the human body for 

 18 */2 years. Passage through rabbits and cattle again increased its virulence. Al- 

 though through animal passage a change of the virulence is possible, nevertheless this 

 change results only inside of the borders of the type and in the direction of the type. 

 The bovine bacillus therefore does not pass into the human type, nor the latter 

 bacillus into the bovine type. 



Only a brief statement will be made relative to the so-called 

 atypical strains. It has been demonstrated that there are cultural 

 strains which cannot be classified as belonging either to one or the 

 other type (Kossel, Weber and Heuss, Lydia Rabinowitsch, de 

 Jong and others). These strains proved to be mixed cultures of 

 both types. In the same person not only mixed infections of both 

 types may exist in the affected organs, but also a double infection 

 may occur in such a way that in one organ the Typus humanus, and 

 in the other organ the Typus bovinus, may be found in pure culture 

 (Weber, Weber and Taute, Griffith, Park and Krumwiede, 

 Steffenhagen). 



In 1901 Koch explained at the International Tuberculosis 

 Congress at London, that tuberculosis of man is produced by a 

 tubercle bacillus which differs from the bovine tubercle bacillus, 

 and expressed himself as opposed to the general prevailing opin- 

 ion of that time, regarding the great danger of the cattle tubercle 

 bacillus for man, and as believing that the transmissibility of 

 bovine tuberculosis to man was so slight compared with the dan- 

 ger which threatens man from tuberculous human beings, that its 

 practical importance was negligible. 



Although Koch's statement cannot stand in the directness of 

 his declaration, nevertheless at the present time it is generally 

 accepted from the above mentioned differential characters, that 

 marked differences exist between the bacillus of bovine tubercu- 

 losis and that of man, and it is a fruitless work to dispute whether 

 they are differences of varieties or peculiarities of the different 

 strains, which lead to the variations, if we accept the fact that the 

 differences of the strains are obstinately retained. 



The results are of especial value in differentiating the two 

 types of tubercle bacilli. In association with Shiitz, Koch under- 

 took some experiments to establish points of differentiation. 



Nineteen calves which were infected intravenously, subcu- 

 taneously, intraperitoneally, by inhalation or feeding experiments 

 with the Bacillus humanus, showed no manifestations of disease, in- 

 creased in weight, and on autopsy conducted several months after 

 infection, showed only caseous purulent changes at the point of 

 inoculation. On the other hand, after the inoculation of bovine 

 tubercle bacilli, severe febrile symptoms and extensive tubercu- 

 losis, especially of the lungs, liver and spleen resulted. The same 

 results were obtained from the experiments of Kossel, Weber, 

 Heuss. Bacilli of the human type were retained in the regional 

 lymph glands ; the changes induced by them gradually retrogressed, 

 whereas infection with the bovine type of the bacillus led to a pro- 



