Tuberculosis. 123 



reaction the temperature begins to rise 10-14 hours after 

 injection, reaches a maximum in 12-14 hours and then 

 declines rapidly. The maximum temperature may 

 reach 105 to 107 F., e. g., 3 to 5 F. above the average 

 normal. An animal is said to have reacted and is looked 

 upon as diseased when the maximum temperature after 

 injection is 2 or more above the average normal tem- 

 perature before injection, or is 1.5 F. above the highest 

 temperature taken before injection. The reaction fever 

 is often so slight that one cannot decide positively from 

 this alone whether the animal is to be adjudged dis- 

 eased or not. In the interpretation of such cases a full 

 knowledge of the conditions surrounding the test, and 

 a history of the animal is of much value. If many other 

 animals of the herd have reacted, a less rise in the case 

 of one or more animals would be classed as a reaction, 

 when it would not be in case no other animals had 

 shown any signs of a reaction. 



Suspicious animals should be retested with a larger 

 dose (3 fold) after a period of 60 days. Animals once 

 tested will not give a proper reaction upon retest if 

 tested within a short time after the first injection. 

 Sufficient time must elapse to permit elimination of the 

 first tuberculin. Animals in the last stages of the dis- 

 ease often do not react. The disease in such animals 

 can usually be diagnosed by a physical examination. 

 During the incubation period of the disease before any 

 diseased tissue has developed, animals do not react to 

 tuberculin. 



The purely mechanical part of the test can be carried 

 out by any intelligent farmer capable of reading ac- 

 curately a clinical thermometer. The interpretation of 

 the test should, however, be made only by an experienced 



