122 



Diseases of Poultry 



ings give much more certain evidence of the existence of this 

 disease. The tubercle is the unit of all tuberculous lesions. 



Fig. 1.3. 



■ Liver of fowl affected with tuberculosis. (After Ward.) 



The tubercles in avian tuberculosis are not essentially differ- 

 ent from those found in mammalian forms of the disease. 

 These tubercles appear as small 

 raised nodules filled with a 

 cheesy substance. 



In birds the organs most af- 

 fected are the liver, spleen and 

 intestinal tract. In some in- 

 stances nearly every organ, 

 including kidneys, ovaries, 

 lungs, bones, muscles and skin, 

 is affected. Statistics collected 

 show that in from 90 to 99 

 per cent of cases the liver shows tubercular lesions (Fig. 

 13). In from 85 to 90 per cent the spleen is affected 



Fig. 14. — Spleen from tubercu- 

 lous fowl cut through the mid- 

 dle. (After Koch and Rabino- 

 witsch.) 



