Avian Tuberculosis. 



613 



tissue mav contain large, yellowisli-white, clieesy foci. The 

 pericardial sac may contain muck fluid while the surtace ot 

 the heart may be covered with flat, grayish-red, raspberry-hke 

 or almost wart-like proliferations (Tietz). Among the other 

 oro-ans, we find, now and then, tuberculous caseous ±oci on 



Fig. 96. Avian Tuberculosis. Caseated foci in the liver and nodules on the 

 intestinal wall. 



the peritoneum, in the kidneys, in the ovaries, in the testicles, 

 in the pericardium and the muscle tissue of the heart, m the 

 air cells, in the gizzard, as well as under the skm and the 

 balls of the feet. 



The histological structure of the avian tubercle is similar in character to 

 that of the mammalian tubercle with the unimportant exception, that by far the 

 greater part of it consists of large epithelioid cells of the foreign-body giant-cell 

 type containing tubercle bacilli and disposed in radial or wreathlike scaly fashion 

 (as seen in section) around the central necrotic mass. The degenerative process ot 

 the tubercle also corresponds more to the hyaline type. Tubercle bacilli are always 

 present in large numbers in the fresh tubercles as well as in the cheesy nodules 

 and in the contents of the involved joints. They are readily demonstrated by means 

 of the usual methods of staining (See p. 5G9). 



