TUBERCULOSIS 



527 



the feed lots. Filthy, manure-covered feed lots, mud-holes, dirty- 

 hog wallows, and similar unhygienic surroundings make the hog 

 more susceptible to the action of the germs and increase the 

 chances for infection by breathing in tubercle bacilli with dust 

 and dirt in the air. 



Improper sleeping quarters, and especially allowing hogs to 

 sleep around a straw or manure pile, increase the chances for 

 tubercular infection. The overheating that results lowers the 



Fig. 82. — -Viscera inspection of hog carcasses by U. S. Government in- 

 spectors. All important organs and glands are carefully examined for 

 evidences of tuberculosis, hog-cholera, and other diseases (U. S. Bureau 

 of Animal Industry Report). 



vitality of the animal, chronic irritation of the lung is set up, 

 and the tubercle bacillus finds a very suitable field in which to 

 develop if it gains entrance. 



Symptoms. — Tuberculosis may, and often does, exist in swine 

 without producing any visible symptoms whatever. The disease 

 is one that develops slowly, and it takes many months for it to 

 make itself plainly evident. It is for this reason that tuberculosis 

 exists in such large numbers of hogs without its presence -even 

 being suspected. It is also largely on account of the fact that the 



