DISEASES OF CATTLE 



277 



What Is Tuberculin? The tubercle bacillus is grown in beef 

 broth containing glycerine. After the maximum growth has 

 taken place, the entire mass of broth and growth is heated to 212 

 degrees F. for 5 to 6 hours. This kills the bacteria and serves to 

 extract the contents of their cells. The dead cells are removed 

 by filtration and the liquid evaporated to one-tenth of its original 

 volume. To preserve it, carbolic acid is added and it is then di- 

 luted for use. It is impossible for the tuberculin to contain any 

 living tubercle bacilli. 



Does the Use of Tuberculin Injure Animals? Tuberculin has 

 no ill effect, whatever, on healthy animals, and no harmful effect 

 on tuberculous animals. It does not, in the amounts used in test- 

 ing, have any effect on the progress of the disease in the animal, 

 nor can it in any way produce the disease. With many of our 

 best herds it has been used regularly for 10 to 15 years with ab- 

 solutely no injurious effects. The statements that the test causea 

 abortion or other ailments are without foundation. The flow of 

 milk is not changed to an appreciable extent, even in the case of 

 tubercular animals. 



How Is the Tuberculin Test Made? The application of the 

 test may be divided into three parts: 1. The determination of the 

 normal temperature of such animal ; 2. The injection of tuberculin ; 

 3. The determination of whether a fever has resulted. 



The Initial Temperature of Two Cows, With Rate of Pulse and 

 Number of Respirations Per Minute. 



Why Is It Necessary to Determine the Normal Temperature? 

 The temperature sf cattle, unlike that of man, varies widely, not 

 only in different animals, but in the same animal at different times. 



