TUBERCULOSIS 



289 



several times larger tluin iiorinal and tlie liver and lungs greatly 

 enlarged. The pleura and peritoneum may bo thickened and 

 covered with tubercles about the size of a millet seed, or larger. 

 Pleural and peritoneal adhesions to the organs within the body 

 cavities are common. 



The tubercle usually undergoes a cheesy degeneration. Old 

 tubercles may become hard and calcareous. Sometimes the cap- 

 sule of the tubercle is filled with pus. A yellowish, cheesy 



Fig. 92.— a section of the chest wall of a tubercular cow showing a better view of the 



diseased tissue. 



material within the capsule of the tubercular nodule or mass is 

 typical of the disease. 



The Tuberculin Test. — The only certain method of recogniz- 

 ing tuberculosis is by this test. There is no other method of 

 recognizing this disease that is more accurate than the above test. 



The substance used in testing animals for tuberculosis is a 

 laboratory product. It is a germ-free fluid prepared by growing 

 the tubercle bacillus in cultiu'e medium (bouillon) until charged 

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