DISEASES AND PESTS OF FOWLS 



drooping wings and tail. Diarrhea is gen- 

 erally one of the symptoms. The comb 

 often turns a dark purple a symptom that 

 has given rise to the name blackhead. 

 Death generally follows an attack fairly 

 rapidly, but in some cases the disease may 

 take a chronic form, while it is believed 

 that recovery is occasionally effected. 



Post-mortem symptoms. The caeca (see 

 Fig. 32) are enlarged, are diseased in parts, 

 and are more or less plugged with cheesy 

 matter and pus. The liver is diseased, 

 being sometimes very much enlarged and 

 covered with yellowish necrotic areas, gen- 

 erally depressed in the centre (see Fig. 24^) . 

 In cases of an acute attack, especially in 

 young birds, one of the caeca only may be 

 affected and the liver may not be invaded. 

 The extent of the necrotic areas and the 

 degree of the enlargement of the infected 

 organs may vary greatly in different cases. 



Cause. The cause of blackhead has been 

 shown by Drs. Cole and Hadley to be a 

 coccidium. A full account of their work 

 is published in Bulletin 141 of the Rhode 



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