COMMON AILMENTS OF CATTLE 157 



the disease escape from an infected animal in the slobber 

 from the mouth, with the manure, and, sometimes in the 

 cast of udder infection, with the milk. As a rule a cow does 

 not die quickly from tuberculosis. The disease usually pro- 

 gresses slowly. The animal may have it for years without 

 any indication of ill health. The disease may attack almost 

 any organ of the animal's body but is common, as with 

 hun i an beings, in the lungs. Animals that have plenty of 

 feed and fresh air may sometimes recover. Good ventilation 

 and good feed and care are important in control of the 

 dise tse. 



It is impossible to tell by external appearances, except in 

 extreme cases, whether the animal is affected or not. For- 

 tune tely we have in the substance known as tuberculin, an 

 agent that is fairly reliable in showing the presence of the 

 disease even in the smallest degree. The test is made by 

 first taking the temperature of each animal three or four 

 times at intervals of two hours. Tuberculin is then injected 

 beneath the skin. After eight or nine hours temperature 

 readings are again taken and repeated five to eight times 

 at two-hour intervals. A rise in temperature suggests that 

 the disease may be present, but experience is necessary for 

 accurate interpretation of the results.. The interdermal 

 method, which is also used, consists in injecting the tuber- 

 culin in soft skin, usually on the under side of the tail. If 

 the disease is present, a swelling appears and remains for 

 several days! 



A dairyman accustomed to the use of instruments can 

 conduct the test himself after first assisting a competent 

 operator. It is safer, however, to have the work done by a 

 trained veterinarian in order that no mistakes may be made 

 and that the test may be recognized by health officers and 



