TUBERCULOSIS. 369 



tion. It was at first thought that the injection was followed 

 by a healing process which would result in curing the disease, 

 and tuberculin was advanced as a remedy for tuberculosis. 

 But, while it appears to have some value in this respect, its aid 

 in curing men from the disease has not been sufficient to war- 

 rant its use, and it has been abandoned for this purpose. 



But the fact that the injection is followed by a rise in tem- 

 perature makes it possible for this material to be used among 

 cattle in detecting tuberculosis. Healthy animals fail to re- 

 spond to this inoculation and are wholly uninjured by it. 

 Possibly there may be a slightly decreased flow of milk for a 

 few days, but this is temporary and unimportant. The farmer 

 may, therefore, have his herd tested with the confidence that 

 his healthy animals will not suffer by the test. On the other 

 hand, the animals that have become infected with the disease 

 will show a rise in temperature, and the test will thus make 

 it possible to separate the affected animals from those that are 

 yet in health. 



The accuracy of the test has been the subject of some dis- 

 pute and is now ascertained as the result of many thousands 

 of cases. It has been found subject to some error. In the 

 first place if animals are tested under abnormal conditions, as, 

 for example, when in new barns, or taken from a cattle car and 

 tested at once, even healthy animals may respond. But when 

 the animals are in normal conditions the healthy animals prob- 

 ably never respond, or at all events so rarely as not to interfere 

 with the accuracy of the test. Secondly, some animals very 

 far advanced in the disease fail to respond. These cases are of 

 little importance since they are commonly detected readily by 

 clinical symptoms. Thirdly, all animals which are moderately 

 attacked, and all of the very incipient cases of tuberculosis, are 

 inevitably detected by the tuberculin. Even a single minute 

 tuberculous gland is sufficient to cause a positive reaction to 

 the test. 

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