DISEASES OF FARM ANIMALS 26;^ 



into a new field, germinate and produce the weed 

 there. Tuberculosis spreads from animal to animal 

 on the same principle that weeds spread from one 

 field to another. 



In order to prevent the spread of tuberculosis it 

 is simply necessary to prevent healthy animals from 

 coming in contact with the diseased ones or eating 

 or drinking after them. 



As tuberculosis cannot be readily detected by a 

 physical examination until the disease is far ad- 

 vanced in the organs affected, it is necessary, in 

 order to determine which animals have the disease, 

 to apply some test or to find the germs of the dis- 

 ease in their excretions. The simplest test that has 

 thus far been discovered is the action of tuber- 

 culin. When tuberculin is injected under the skin 

 of the animals affected with active tuberculosis the 

 animals respond by a rise of temperature, which 

 follows a somewhat definite curve. By means of 

 this test it is possible to pick out the infected in- 

 dividuals so that they can be separated from the 

 healthy ones. The test should be repeated in from 

 six months to a year in order to detect any new 

 cases which might have developed from latent or 

 arrested ones. We cannot always get all of the 

 infected animals with the first test any more than 

 we can always remove every weed from the garden 

 by one hoeing. 



The Bang Method for the Control of tuberculosis 

 consists in separating the animals that are infected 

 from the well ones and keeping them for breeding 

 purposes. The calves are removed from their dams 

 as soon as born and fed with the milk of healthy 

 cows, or the pasteurized milk of the infected ones. 

 It has been found that but a small percentage of 

 calves that are raised under proper precautions from 



