THE CONTROL OF TUBERCULOSIS 145 



years ago. Its complete eradication can only come through united 

 action. To get this action every dairyman must understand why 

 sound and profitable dairying demands that his herd be free from 

 tuberculosis. 



223. The losses.— The disease takes a regular toll by death 

 from herds where it has become established. Long before death it 

 lowers the usefulness of the animal and makes her an unprofitable 

 producer. Once tuberculosis gets into the herd it spreads from 

 animal to animal. The calves become infected through the milk 

 and the pigs also fall victims if fed dairy by-products. Tubercu- 

 losis destroys the reputation of the herd, making it difficult to sell 

 either the animals or the milk. An animal showing physical signs 

 of tuberculosis has practically no market either for milk production 

 or breeding. More and more buyers are demanding animals 

 shown by test to be free from the disease. With the realization of 

 the possibility of the spread of the infection to children through 

 the milk, the consumer is commencing to demand milk from tuber- 

 culosis-free herds and public health officials are giving this subject 

 increasing attention. 



224. Nature and symptoms.— Tuberculosis in cattle is 

 similar to the disease in man. It is caused by a germ which grad- 

 ually eats away the tissues of the body. The process may go on 

 for four or five years before the presence of the disease can be 

 recognized by any physical or external symptoms. The germ gets 

 into the body in the air breathed in or may be taken in with the 

 feed. When breathed in, it goes directly to the lungs which we 

 frequently think of as the principal seat of the disease, and from 

 the lungs gets into the blood. When taken in with the feed it gets 

 into the blood through the digestive tract. Once the germ gets into 

 the blood, any part of the body may be attacked. Thus, we 

 have tuberculosis of the joints, of the udder, etc., as well as of 

 the lungs. 



225. How the disease starts. — The germs float around on the 

 dust in the air and may live in the cracks of the mangers and in 

 other places around the barn for months. These germs must come 

 from some animal which is giving them off. The}- are given off in 



