454 MILK 



not react, but in such cases physical examination is reliable. 

 Sometimes animals but slightly affected do not react, the tubercle 

 not having developed typically (occult tuberculosis) ; on the other 

 hand, reacting animals sometimes fail to show lesions on post- 

 mortem examination. In the hands of experienced and careful 

 veterinarians, however, it rarely happens that lesions are not 

 found in reacting animals. The percentage of failures is really 

 very small and cannot be used successfxilly as an argument agamst 

 the efficiency of the tuberculin test. 



The use of tuberculin as a diagnostic means for tuberculosis 

 has aroused much antagonism among producers. Among the 

 prejudices existing is the claim that tuberculin has caused dis- 

 eases and abortions in cows. Careful observation has invariably 

 failed to confirm such claims. Abortion is a common malady 

 among cows and has never been successfully traced to tuberculin 

 injections. The fever produced by tuberculin in reacting animals 

 and other sUght derangements disappear, as a rule, in forty-eight 

 hours. Another source of prejudice is the immunity caused by 

 the injection of tuberculin. This immunity may last for six weeks. 

 An animal retested during this period will not react, and producers 

 have used this phenomenon as an argument against the relia- 

 bility of tuberculin. Unfortunately, this same immunity has 

 been created in cattle by unscrupulous dealers. The purchaser of 

 cattle that are "doped" with tubercuKn finds them immune when 

 tested and believes them to be free from the disease. A subse- 

 quent test then shows the deception. In any case it is essential 

 that a reliable preparation be used for this test. 



The producer often fails to realize that a herd free from tuber- 

 culosis is more productive of profit than an infected herd. Al- 

 though tuberculous cows in the initial stages of the disease may 

 yield normal quantities of milk, their period of usefulness is rela- 

 tively short, and consequently the profit to the producer not what 

 it might be. The same argument holds good for beef cattle. 

 However, the temporary loss is sometimes enormous, and it is 

 only fair to the cattle owner that the community bear part of the 

 loss caused by slaughtering consumptive cattle. Unless the dis- 

 ease is far advanced the beef value remains. Tuberculous cattle 

 are condemned as food only when they are in advanced stages of 

 the disease. Danger to human health from the use of infected 

 meat is slight, since the bacilU are destroyed by cooking — roast- 

 ing, for example. When the carcase is a total loss an in- 

 demnity should be paid by the state or city. Only by such 

 means is it possible to interest the producer in freeing his herd 

 from tuberculosis. At best, this is a lengthy and expensive 

 process. The antagonism of producers has led in a few cases to 



