162 LIVESTOCK ON THE FARM 



or get into the blood and be carried to other parts. Where one 

 of these germs lodges and starts to grow it forms a colony. 

 This produces a swelling. The germs continue to grow on the 

 outside of this swelUng. Finally the germs in the interior of 

 the swelhng die and produce pus. Sometimes pus dries. 

 The disease consumes the tissue of the animal and gives off 

 poisonous products. 



Tuberculosis will destroy an animal in time and will spread 

 from one animal to another in a herd. Great care should be 

 exercised in buying animals that are tested and free from the 

 disease. A dairy herd also should be tested every year to 

 make sure that it is free from the disease. If any animals are 

 found that react to the test (have the disease), they should 

 at once be disposed of or isolated from the rest of the herd. 



Different States have different laws for disposing of tubercu- 

 lous animals. Some States kill them and pay a fixed sum. 

 The State livestock sanitary board, if there is one, should be 

 consulted. At any rate, tuberculous cows can be sold on the 

 regular market for slaughter where they pass government 

 inspection. Only about one-tenth or less of tuberculous 

 cows are entirely condemned as unfit for human consumption. 

 The disease is often light and confined to the lungs and in- 

 testinal glands which are destroyed. Where the disease has 

 spread through the entire carcass, the whole is condemned, 

 and it is used for the manufacture of fertilizers. Valuable 

 breeding cows that have the disease can be kept for breeding 

 purposes by keeping them isolated. 



Tuberculin Test. — There is no cure for tuberculosis. The 

 tuberculin test is a means of testing cows for tuberculosis to 

 detect the presence of the disease. The test is usually ap- 

 plied to cattle by veterinarians but anyone can apply it. 

 The agency employed is tuberculin. This is prepared from 

 the germs that cause tuberculosis, the tubercle bacilli. These 

 are cultivated artificially and then an extract is taken and this 

 is treated with a solution of carbolic acid. Tuberculin is 

 entirely free from tubercle bacilli or any other germs, and can 

 be obtained from the State livestock sanitary board or from 

 commercial firms. 



In performing the test, cows are kept under normal condi- 



