Tuberculosis. 297 



ability in tubercle bacilli derived from human beings and from 

 various types of animals, referable to the source of the virus. For 

 example, as shown by R. Koch and Schiitz in a long series of experi- 

 ments, and even earlier by Putz (1882) and Smith (1896), it is not 

 as a rule easy to render cattle, sheep and swine tuberculous by 

 using tubercle bacilli from a human source (even in case of inoc- 

 ulation of large quantities) ; and it is also difficult to infect birds 

 with tuberculous material derived from man or mammals. These 

 negative results at first caused doubt as to the identity of the tuber- 

 culosis of all individuals. However, it was recognized that no dis- 

 tinct line of difference could be drawn between the organisms, for 

 even a few positive results were sufficient to show the identity of 

 the affection in man and in animals. Positive cases of the kind re- 

 quired have been obtained in such abundant number and from ex- 

 periments of indisputable accuracy that the possibility of infecting 

 man with bovine tuberculosis and of the transmission of human 

 tuberculosis to the domestic animals cannot be denied. Besides the 

 older experiments of Bollinger, Klebs, Chauveau and the later ones 

 of Sidney Martin, Frothingham. Arloing. de Jong, Stuurmann, 

 Thomassen, Prettner, Klebs and Rievel who were successful in 

 inoculating cattle with tuberculous virus from man, tlie examples 

 collected by Johne. Ostertag and Xocard and Leclainche of wound 

 inoculation in man, occasionally actually occurring in the 

 course of slaughtering operations and meat inspection, speak 

 strongly for the idea that bovine tuberculosis is an infection of no lit- 

 tle importance to man. Important contributions have also been made 

 in this connection by Johannes Fibiger and C. O. Jensen, goihg to 

 show that tubercle bacilli virulent to man may also be highly viru- 

 lent to cattle, and confirming the belief that many cases of intestinal 

 tuberculosis in children are properly attributed to the ingestion of 

 cow's milk containing tubercle bacilli, von Behring arrives at the 

 same conclusion, finding that some strains of tubercle bacilli obtained 

 by culture from human source possess high grade of virulence for 

 cattle while other strains have no pathogenic influence for cattle 

 at all. Further the observations made by Eberlein and Cadiot, in- 

 dicating the acquirement by man of the infection from tuberculous 

 parrots and the rather common transmission of the disease to parrots 

 from consumptive human beings, as well as the transmissibility by 

 inoculation of bovine tuberculosis to apes, proved by Nocard, force 

 the assumption of an ^etiological relationship of the disease or of a 

 family identity of the tubercle bacilli of heterogeneous derivation. 

 [Recently Koch has brought forward anew the idea of specific dif- 



