88 POULTRY DISEASES 



year, although I have seen the disease in birds that 

 were much older. Several outbreaks have been 

 studied in this laboratory. Only one case was 

 found in the hen. It has been reported in the pea- 

 cock. 



Fig. 29. Section of the Liver (from a Case of Blackhead) 

 a, Protozoa causing the' disease, b, a giant cell. 



The symptoms are not manifest till tlie disease 

 has progressed to a considerable extent. The bird 

 is first noticed to be dull, later the wings and tail 

 may droop; the feathers become ruffled and the 

 bird sits around much of the time ; diarrhea super- 

 venes, the discharge being of a greenish-yellow 



