22 BULLKTIX 150. 



The animal with local tubercle may not at the present time be 

 diffusing the poison, but where such animals are preserved one 

 will at intervals have the local tubercle extended so as to cause 

 generalized tuberculosis ; and as this extension necessarily takes 

 place by the conveyance of the bacillus through the blood, and 

 as such bacilli must be circulating in the blood before they can 

 invade new tissues and form new tubercles, it follows that there 

 is always a period between the entrance of such bacilli into the 

 blood and the development of new tubercles in which the blood 

 and all blood-containing organs are infecting, though no symp- 

 tom nor lesion of new tubercles can be detected. At this 

 stage the animal may convey tuberculosis through its flesh, 

 or through its dairy products, while even a post mortem exam- 

 ination would pronounce it free from generalized tuberculosis. 

 It is also liable to distribute the germ to other members of the 

 herd before any suspicion of immediate danger is entertained. 



Deduction. It may be concluded from such considerations as 

 the above that the tuberculin test is indispensible where one 

 aims at a guarantee of the soundness of the progeny and dairy 

 products of a herd, but that its use demands one of two conditions. 



A. That the animals showing tuberculosis under the test 

 shall be destro\'ed and the buildings where they have been shall 

 be disinfected ; or, 



B. That such infected animals, as have the disease in a latent 

 form, shall be formed into a separate herd and kept well apart 

 from other stock, for breeding purposes only ; or if their milk is 

 used that it shall be first subjected to sterilization. 



The stockowner who values the sound portion of his herd can- 

 not afford to allow even the latent cases of tuberculosis to min- 

 gle with it. 



TUBERCULIN IN MODERATE DOSE HARMLESS TO 



SOUND CATTLE. 



The concurrent testimony of all veterinarians drawn from 

 hundreds of thousands of tests is that the ordinary test dose is 

 harmless to a nontuberculous animal. In 1894 I put this to 

 a crucial test on five cows (Holstein, Jersey and grade) injecting 

 the tuberculin on six successive occasions and found that it pro- 



