TuBERCUIvOSIS. 133 



from which it is derived. Thus the virus from the ox which proves 

 certainly fatal to the guineapig on inoculation, cannot be suc- 

 cessfully inoculated under the skin of the guineapig after it has 

 passed through several generations in as many birds, but if inocu- 

 lated from the bird in the abdomen of the guineapig and con- 

 tinued for several generations in this rodent it reacquires all its 

 former potency (Nocard, etc.). So to a less extent with cattle ; 

 from one cow the inoculation invariably produces the disease ; 

 from another only occasionally. The same must hold in feeding. 

 4th. The degree of infection of the material fed has much in- 

 fluence. Tuberculous glands, and tubercles whether recent or 

 caseated are of course the most certainly infecting. The blood 

 and red flesh (in the ox) may be said to be the least frequently 

 infecting, while the infecting power of milk will vary according 

 as the udder is or is not the seat of tubercle. Toussaint who 

 seems to have met with especially virulent cases inoculated suc- 

 cessfully with the blood, nasal discharge, bile, urine, tears, flesh 

 juice, dung, etc., of a tuberculous cow. Others like Nocard and 

 McFadyean have failed with blood and flesh juice. The danger 

 may be estimated by taking a middle position. It may be well to 

 consider the blood, flesh and milk separately. 



Dangers from Blood. 



It cannot be denied that blood is inimical to this bacillus as to 

 most other microbes. Even if the virus is injected into the veins 

 in such quantity as to produce general tuberculosis, the germs 

 become largely arrested in different organs or robbed of their vir- 

 ulence so that in a few days the blood is comparatively little 

 infecting. This does not, however, do away with the fact that 

 the injected bacilli live long enough in the blood to produce tuber- 

 cles in many different organs, and the same is true when the dis- 

 ease extends from single primary tubercles, to a general tubercu- 

 losis ; in most cases the bacilli can only have travelled through 

 the blood. Bang found that of 20 cows in advanced tuberculosis, 

 the blood of only two (or 10 per cent.) proved infecting when 

 inoculated. Nocard has never succeeded in producing the disease 

 by injecting the blood of a tuberculous ox into the abdominal 

 cavity, yet he recognizes that as the disease extends by means of 

 bacilli conveyed by the blood, this liquid must be infecting wher- 



