DISEASES OF FARM ANIMALS 265 



intestines; udder and generative organs. The 

 membrane covering the lungs (pleura), the heart 

 (pericardium), and intestines (peritoneum), are 

 frequently affected. It often happens that a large 

 mass, or masses, of tuberculous tissue grow over 

 one or more of these membranes. The most pecu- 

 liar thing about bovine tuberculosis is the fact that 

 frequently an animal v^ill appear to be perfectly 

 well, but when slaughtered will be found to have 

 a large number of tuberculous areas or masses on 

 the membranes or in its organs. The reason for 

 this is that the diseased area is not at a vital point. 

 The organ or membrane affected depends upon 

 the one to which the germ is carried. Usually 

 animals are infected in but one organ in the be- 

 ginning, and from this diseased area the germs 

 spread through the blood vessels or lymph chan- 

 nels to other organs. When the diseased area is 

 restricted to one organ or part, it is called " local- 

 ized " tuberculosis, because it appears at the point 

 where the seed or germ was first planted. When 

 the germs spread through the circulation from 

 this first or primary diseased area to other organs 

 and set up new tuberculous growths, the con- 

 dition is called " generalized " tuberculosis. When 

 cattle are slaughtered for food, if they are found 

 to be afflicted with localized tuberculosis, the flesh 

 is considered to be fit for food, but if the disease 

 is generalized the carcass is condemned. 



The Symptoms of Tuberculosis vary according to 

 the location of the disease. If it is in the glands of 

 the throat it is suggested by their enlargement. If 

 it is in a gland about the lungs, which, because of 

 its enlargement, presses on the oesophagus (gullet), 

 there might be bloating. If the disease is in the 

 lung tissue there would be, after it is sufficiently 



