Bovine Tuberculosis. 



117 



able results with it. All those who have worked with tuberculin are 

 agreed that it is one of the safest and surest tests in detecting the presence 

 of active tuberculosis that is known to the medical world. All are agreed, 

 however, that it must be properly used, and that all those physical con- 

 ditions that would tend to interfere with it must be avoided. If in its use 

 these precautions are taken, tuberculin is as sure as any reagent. . 



If the animal is sound when tuberculin is injected, no reaction is 

 observed. If, however, the animal contains an active tubercle there is a 

 reaction which shows itself in a rise of the temperature beginning from 

 six to sixteen hours after the injection and continuing for from six to ten 

 hours and possibly longer. Fig. 134 shows the curve of the temperature 

 reaction after injecting the tuberculin in a tuberculous animal. There is 

 in some cases a general depression in the appearance of the animal in addi- 

 tion to its elevations of temperature. 



The interpretation of the temperature record requires care. If, how- 

 ever, all conditions pertaining to the protection of the animal have been 

 fulfilled, the temperature curve mentioned is a very sure indication that 

 the animal is suffering from an active, although it may be a very small, 

 tuberculous growth. A good reaction will take place when the active 

 tubercle is so small that it is difficult to see it. The so-called failures to 

 find the disease after the reaction 

 have been due in many cases to the 

 fact that the bone marrow, brain 

 and inter-muscular tissue were not 

 carefully examined. Small lesions 

 in the lymph glands are also easily 

 overlooked. If there is no reaction 

 the correct interpretation is more 

 difficult. In this case there are 

 three conditions which must be 

 taken into account, namely : 



(i) If the animal is extensively 



diseased, it may not react. In this 



case the physical condition would 



show that the animal was at least Fig. 1^3.— The germs or bacilli that cause 



, 1 1^, rx-, , tuberculosis. Much magnified. 



not healthy, there are a number 



of cases on record where the tuberculin was accused of failing to react 



when the disease present was not tuberculosis at all but actinomycosis, 



fungous diseases, or other disorders resembling somewhat in appearance 



a tuberculous condition, 



(2) If the test was made during the period of incubation there would 



be no reaction although the disease may soon develop. To overcome this 



danger, a subsequent test should be made in from three to six months. 



