TUBERCULOSIS 287 



after sixty days. If the retest is made at an earlier time, it 

 is likely to be less reliable, owing to the effect of the tirst 

 dose of tuberculin. On the retest a triple dose of tubercu- 

 lin should be used, and the temperatures after the injection 

 should be begun by the fourth hour, since the reaction is 

 likely to appear earlier than in the original test. 



Animals recently infected but not yet containing diseased 

 tissues, i. e., those in the incubation stage or those in which 

 the disease is dormant, do not as a rule react to the test, 

 while those in which the disease is far advanced often .fail 

 to react because they are already saturated with the tuber- 

 culin naturally formed as a result of disease. 



The disease in the latter can be recognized by a physical 

 examination ; in the former only by a repetition of the test 

 at intervals so as to determine its presence before it has 

 made such headway as to make the animal a source of 

 danger. 



The purely mechanical part of the test can be carried out 

 by any intelligent farmer. He should learn how to read the 

 thermometer accurately and acquaint himself with all the 

 details of the test. No farmer need neglect the testing of 

 his herd because of the inability to obtain a veterinarian, 

 or on account of expense. The advantage of being able to 

 test one's own herd is great, since retests can be made on 

 single animals as the occasion seems to warrant, and all 

 animals purchased can be tested before they are placed 

 with the herd. 



Freeing the herd from tuberculosis. The methods to be 

 followed depend on the value of the animals, and the extent 

 of the disease in the herd. If but few animals are found 

 to be infected, the cheapest and most effective way is to 

 remove them. If a larger portion is diseased, and espe- 

 cially when the animals are valuable for breeding purposes, 

 the herd may be separated into healthy and reacting sec- 



