422 THE MANAGEMENT AND FEEDING OF CATTLE 



Costly experience has shown that even one tuberculous 

 animal is a menace to all the animals kept in the same 

 stable. How much greater, then, must the hazard be 

 with many diseased animals in the same stable? Within 

 a few months, how many is not certainly known, from 

 the time the germs reach the animal, cattle will 

 respond to the tuberculin test. 



Tuberculosis has, it is thought, been more prevalent 

 among dairy cattle than in beef types, owing, first, 

 to the tax which much milk giving puts upon the sys- 

 tem, and, second, to the close confinement to which they 

 are subjected in winter. In city dairies it is more prev- 

 alent than in farm dairies, owing to the more frequent 

 introduction of cows from outside sources. In the pure 

 breeds of beef cattle it is more common than among 

 grades, owing to the more artificial conditions to which 

 they are subjected. It has been present in greatest 

 degree among the families of pure-breds that have been 

 much inbred, as in certain families of the Shorthorn, 

 Aberdeen-Angus, Jersey, and Guernsey breeds. It de- 

 creases as open range conditions of environment are 

 approached, thus showing the closeness of the relation 

 between abundant fresh air, ample exercise and plenty 

 of sunlight and the absence of tuberculosis. 



Tuberculin is usually seen in the fluid form. It is 

 a chemical product obtained from the bodies of the 

 bacilli of tuberculosis. It is excreted by the tubercle 

 bacillus during the process of growth. It is germ free, 

 and, therefore, cannot communicate the disease. Care- 

 ful experiment has shown that tuberculin has no im- 

 portant influence favorable or unfavorable to the health 

 of sound cattle or to the milk flow of healthy cows. 

 Making the test calls for two days. The temperature 

 of the animal or animals is taken the first day at inter- 

 vals of two to four hours, usually commencing at 8 a. m. 

 and ending at 8 i'. m. At 9 P. m. the tuberculin is given 

 by hypodermic injection. Temperatures are taken again 



