BACILLUS OF TUBERCULOSIS. 299 



authorities in adopting the necessary hygienic measures 

 to stamp out tuberculosis entirely; but, judging from 

 the results which have already been obtained in reducing 

 the mortality from this dread disease, we have reason to 

 believe that in time it can be completely controlled. 



The Tubercle Bacillus of Cattle and its Relation to 

 Human Tuberculosis. Among the domestic animals 

 tuberculosis is most common in cattle. On account 

 of the milk which they provide for our use, and which 

 is liable to contain bacilli, the relation of these to human 

 tuberculosis is a matter of extreme importance. 



The chief seat of the lesions is apt to be the lungs 

 and with them the pleura; less often the abdominal 

 organs and the udder are affected. In pigs and horses 

 the abdominal organs are most often involved, then the 

 lungs and lymphatic glands. In sheep and goats tuber- 

 culosis is rare. The bovine bacillus, as the most im- 

 portant of the group, will be alone considered here. 



The bacilli derived from cattle are on the average a 

 little shorter and straighter than the average human 

 bacillus; but there are many derived from cattle exactly 

 similar to those derived from man in size, shape, and 

 staining. In guinea-pigs, and especially in rabbits, the 

 bovine bacilli are more virulent than those from human 

 sources. Animals infected with the bacilli from cattle, 

 as well as those from the other domestic animals, react 

 to the tuberculin test. All these bacilli are, therefore, 

 undoubtedly from the same original stock, and at 

 first glance we might consider it unnecessary to prove 

 that those derived from cattle were capable of causing 

 human tuberculosis. There are facts, however, which 

 tend to make us doubtful of the extent to which this 

 infection takes place. As we investigate we find that 



