478 ANNUAL REPORT OF THE Off. Doc. 



It cauuot be deuicd that w bat may be called bovine tubercle bacilli 

 are as a rule disLinetlj more viiuleut for cattle and other domes- 

 ticated auimals than Jiunjan bacilli, or that the results of experi- 

 ments indicate that in natural circumstances there is little danger 

 of cattle becoming infected from humau beings, liut it cannot be 

 admitted that the low virulence of human bacilli for cattle proves, 

 or even makes it probable, that bovine bacilli have only a feeble 

 pathogenic power for man. That might have been held to be proba- 

 ble if it had been shown that bovine bacilli were very virulent only 

 for cattle, but since it is well established that these bacilli are highly 

 dangerous for such diverse species as the rabbit, horse, dog, pig and 

 sheep, a4id in short, for almost every quadruped on which they have 

 been tried, it appears to be highly probable that they are also dan- 

 gerous to man. At any rate it is impossible to cite any ascertained 

 fact relating to other bacterial diseases that makes the contrary con- 

 clusion probable. It is well known that the majority of disease-ex- 

 citing bacteria are harmful to only one or two species, but all those 

 that are common to all the domesticated animals are also pathogenic 

 to man. 



With regard to the vic^w that the difference between humao and 

 bovine bacilli in respect of virulence for cattle is of such a fixed and 

 constant character thai it may be relied. ux)on to distinguish the one 

 from the other, it need only be said that that is very far from proved. 

 It appears to be quite possible that what may be called the normal or 

 average virulence of bovine bacilli for cattle may be reduced by pas'- 

 sage through the human subject. Besides, there are very great dif- 

 ferences ill the virulence of tubercle bacilli found in animals of the 

 same species, and ii' a low degree of virulence for cattle is to be taken 

 as the distinguishing feature of human bacilli, there will be no diffi- 

 culty in proving that the human disease is sometimes transmitted 

 to the lower animals. 



The third proposition in Dr. Koch's argument is J he only one which 

 is really germa-iie to the point at issue, viz., that only cases of prim- 

 ary intestinal tuberculosis can possibly have had their origin in in- 

 fected milk or meat, and that "such cases are extremely rare." Dr. 

 Koch refers to several large series of post-mortem observations that 

 appear to justify this statement, and adds that he could have cited 

 many more pointing to the same conclusion. Now, if it were a fact 

 that all the statistics relating to this point were unanimous, it 

 would have to be admitted that primary intestinal tuberculosis is 

 rare in the human subject, a<»d that cases of infection through milk 

 are still rarer, though even then it might be advisable to take meas- 

 ures to prevent the few cases. ]?ut the statistics are not by any 

 means unanimous, and those that are likely to appeal with most 

 force to the people in this country are not at all in accord with those 

 quoted from Germany. During the last few years the evidence ob- 



