SPECIFICITY OF TUBERCULOSIS 227 



International Conference on Tuberculosis in Berlin.^ He again 

 emphasised the comparative rarity of primar>^ intestinal tuber- 

 culosis in the human being, and the local, as distinguished from the 

 general, infective nature of accidental bovine inoculation of man 

 {tuberculosis verrucosa cutis). In isolated cases the nearest lymph 

 glands might become affected, but the disease remained neverthe- 

 less a local one. Dr Koch further expressed the view that if 

 bovine tuberculosis was transmissible to man by means of the 

 milk of cows with tuberculous udders, it would be reasonable to 

 suppose that "groups of illnesses" would occur, in a manner 

 analogous to other infective diseases, though the circumstances 

 would differ owing to the different length of the incubation periods. 

 By way of illustrating the non-infectivity of bovine tubercle bacilli 

 conveyed by milk, Koch points out {a) that bovine tubercle bacilli 

 must be taken into the human system very frequently, as i to 2 per 

 cent, of all milch cows suffer from tuberculous udders ; (Jj) that in 

 addition to being drunk in considerable quantity and for long periods, 

 such milk is also widely distributed ; (<:) that domestic sterilisation of 

 milk does not occur to any appreciable extent ; {d) that the same 

 may be said of the large dairies ; and finally {e) that if milk under 

 such circumstances is dangerous, the butter derived from it will 

 also be dangerous. For these reasons he maintained that any 

 resulting disease must be widespread. Yet Koch has found 

 " instead of the countless cases," which we ought to expect, " two 

 groups of illnesses and 28 isolated cases of illness." On examina- 

 tion he finds most of these recorded cases not free from objection. 

 To carry conviction as to milk-borne tuberculosis, Koch main- 

 tains, that the following conditions must be fulfilled : — (i.) 

 Certain proof of tubercle in the person affected ; (ii.) exclusion of 

 other sources of infection ; (iii.) the condition of all the consumers 

 of the suspected milk ; (iv.) the exact source of the suspected milk, 

 particularly in respect to the disease of the udder of the cow 

 yielding the milk. Finally, he concludes that all that can be said 

 at present is that the injurious effects of milk infected with bovine 

 tuberculosis and its products are not proven. 



On the other hand, it must be said that a number of investiga- 

 tors have already brought forward fresh evidence in support of 

 the view previously held that human tuberculosis is transmissible 

 to animals, and, prima facie, the reverse proposition, that bovine 

 tuberculosis is transmissible to man. Among the workers who 

 have thus by later experiment, already thrown doubt upon 

 ^ Brit. Med. Jour., 1902, vol. ii. (20th December), p. 1885 et seq. 



