232 POPULAR SCIENCE MONTHLY 



The early observations of the Italian investigators, Rivolta and Mafueci, 

 have been confirmed and so extended as to give us a fairly comprehen- 

 sive knowledge of the capacities for pathogenic action, upon different 

 animal species, of the avian bacilli. At the same time painstaking 

 studies of the degree to which birds are subject to inoculation with 

 pure cultures of tubercle bacilli of human origin support the view of 

 diversity in type of bacilli and susceptibility of species. And yet, while 

 fowl react only with slight local lesions, as a rule, to inoculations of 

 tubercle bacilli of human origin, certain mammals have proved them- 

 selves fairly subject to experimental inoculation with avian bacilli. 

 While the guinea-pig, otherwise so sensitive to inoculation tuberculosis 

 with the mammalian bacilli, is relatively resistant to the avian variety, 

 the rabbit, which exhibits a marked degree of refractoriness to the 

 human bacilli, succumbs quite readily to the avian bacilli. It is, how- 

 ever, worth noting that the reactions in the rabbit which avian tubercle 

 bacilli call forth do not conform to those observed in tuberculosis in 

 general; there is absence of typical tubercles and caseation, and the 

 chief pathological alterations observed are found in connection with 

 the enlarged spleen. 



The literature on tuberculosis contains a small number of references 

 to the cultivation from human subjects of the avian tubercle bacillus. 

 From our present knowledge it may be postulated that avian tubercle 

 bacilli occur rarely in man. Eabinowitsch has, indeed, recently empha- 

 sized the occasional occurrence of the avian bacilli in cattle, swine, 

 horses and monkeys; but they constitute a small source of danger in 

 the spread of tuberculous disease among mammals. The parrot, because 

 of its use as a pet and of its susceptibility to the avian bacillus, on the 

 one hand, and of the human bacillus, on the other, is a greater menace 

 to public welfare. 



The subject of bovine tuberculosis and of bovine tubercle bacilli 

 is among the most important of all the questions relating to the sup- 

 pression of tuberculosis. The admirable studies of Theobald Smith 

 established the distinction in type subsisting between certain bacilli 

 of human and of bovine origin. We have come now to regard these 

 types as separate and not to be transmuted, at least not readily under 

 artificial conditions of cultivation, into each other. Into the disputed 

 questions of variation due to environment I can not afford to enter. 

 But I would have you believe that transformations of avian, bovine and 

 human bacilli into each other have probably not been accomplished by 

 experimentation. The cultivation of one variety of bacilli in the body 

 of an alien species has been said to alter profoundly the properties of 

 the bacilli; but the observations upon this point are in my opinion far 

 from convincing. The mere fact that avian and bovine varieties of 

 bacilli preserve their peculiar properties when occurring naturally in 



