Tuberculosis of Man and of Animals. (319 



bovine types into the avian type. This was particularly evident when 

 a fowl passage was preceded and followed by a guinea pig passage. 

 Bang observed also that a bovine strain which had lost its virulence 

 after long continued or oft repeated passage through fowls, regained 

 its virulence by passage through goats. 



These positive results of experimental investigations, even 

 though not very mimerons, cause doubts to arise in regard to 

 the supposed specific differences between the bacilli of mam- 

 malian and avian tuberculosis. If we consider in connection 

 with the foregoing that Hericourt & Ricliet immunized monkeys 

 and dogs against human tuberculosis with avian virus and 

 that MacFadyean and Behring immunized cattle against bovine 

 tuberculosis by the same means, and further that effective 

 tuberculin may be prepared from avian bacilli (according to 

 Maffucci cattle and sheep will react to human tuberculin, no 

 matter whether they were infected in the first place with bovine 

 or w^ith avian bacilli), that mammalian and avian bacilli ex- 

 hibit reciprocal agglutination characteristics, and finally that 

 it is possible to produce, experimentally, avian tuberculosis 

 in mammals and mammalian tuberculosis in birds, the conclu- 

 sion that the avian bacillus is merely a variety of Koch's 

 bacillus resulting from prolonged growth for numberless 

 generations in the bodies of fowls is probably justified. Ac- 

 cordingly, avian tuberculosis might be looked upon as bearing 

 a similar relation to mammalian tuberculosis as human tuber- 

 culosis bears to bovine tuberculosis. 



Tuberculosis of Man and Tuberculosis of Mammals. These 

 two diseases have in recent times been looked upon as etiolog- 

 ically identical notw^ithstanding the fact that conspicuous dif- 

 ferences have been observed to exist in the pathogenicity of 

 strains of different origins. Though Puetz, as early as 1882, 

 doubted the identity of human and bovine tuberculosis because 

 he was unsuccessful in infecting calves either by feeding or 

 with intravenous or subcutaneous injections of human tuber- 

 culous material and Semmer (1893) expressed the opinion that 

 pearl disease and miliary tuberculosis of man w^ere not identical 

 morbid processes, later authors assumed upon the basis of- 

 occasional negative results in the experimental transmission 

 of the tw^o diseases to other animals that this difference must 

 be due to modifications in the virulence of an essentially 

 identical virus and to the variable relative susceptibility of 

 the different species of animals. 



Th. Smith had observed certain morphological and cultural differ- 

 ences between human and bovine bacilli and demonstrated that the 

 bacillus of pearl disease had a considerably greater and more constant 

 pathogenic action on experiment animals than that of human tuber- 

 culosis. He believed, therefore, that the bacillus of bovine tuberculosis 

 occupied a unique position among the various mammalian bacilli and 



