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 _ biackhead. 
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 ceca (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. 24d). 
In cases of an acute attack, especially in 
young birds, one of the ceca 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 
31 
