TUBERCULOSIS 81 



dangerous to health. Therefore, it must be one of the 

 most important purposes in milk control to prevent the 

 sale of such milk. 



It is a difficult task to detect tubercle bacilli in milk. 

 Intraperitoneal injections of the milk into guinea pigs 

 and rabbits may be made, but sometimes many of the 

 animals die from other infections (cocci; other bacteria). 

 Sometimes so long a time elapses before the results are 

 available that the experiment has lost much of its prac- 

 tical value. Moreover, certain similar bacteria (acid- 

 fast bacteria) may cause alterations in the experimental 

 animals which can hardly be distinguished from tuber- 

 culosis. The detection of tubercle bacilli in milk by 

 microscopic examination is difficult; a direct examina- 

 tion will very seldom give results ; so one must depend 

 either on centrifuging, whereby all the little flakes to 

 which the bacilli usually adhere may be thrown down, 

 and then examined, or other means for separation must 

 be used (see below) so that the bacilli may be precipi- 

 tated without too great a quantity of sediment. 



Since the number of tubercle bacilli in mixed milk is, 

 at most, but small, only a positive result of the examina- 

 tion can be final, and even then the result is doubtful 

 since, as mentioned before, " pseudotubercle bacilli " 

 may appear in milk (see below) which are like the tuber- 

 cle bacilli in respect to staining and are similar also in 

 morphology. 



We must, therefore, depend on the clinical examina- 

 tion of the cows in the herd itself, if we would check the 

 passage of tubercle bacilli into milk. This inspection 

 must be directed especially to tuberculosis of the udder, 

 uterus and intestines and, at the same time, to miliary 

 tuberculosis and to all cases of lung tuberculosis suf- 

 ficiently developed to cause the appearance of clinical 

 signs. But the inspection must not be clinical alone ; in 

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