DISKASES OF POULTRY. 



185 



crashed into powder. A microscopic examination of 

 this powder reveals numerous mites and the debris 

 which they produce. 



The disease appears in poultry -yards as a conse- 

 quence of the introduction of one or more birds al- 

 ready affected. It is 

 teadily c o m m u n i 

 cated, develops rapid- 

 ly and in a few days a 

 whole flock is con- 

 taminated. It usually 

 begins on the rump, 

 the transfer of con- 

 tagion being effected 

 by copulation, and 

 spreads rapidly to the 

 back, the thighs and 

 the belly. An infest- 

 ed cock will rapidly 

 infect all the fowls in 

 a poultry -yard. Often 

 the head and the up - 

 per surface of the neck ^re affected early in the 

 course of the disease. The feathers fall off at all 

 these points, and finally the skin is denuded over a 

 large extent of surface. The large feathers of the 

 tail and wings and the wing -coverts are generally 

 retained. 



The denuded skin presents a normal appearance — 

 it is smooth, soft, of a pinkish color and not percepti- 

 bly thickened. By pulling out the feathers which 

 remain near the invaded parts, it is easy to find, with 

 both fowls and pigeons, a mass of epidermic scales at 



Fig. ^^.^-Epidermoptes bilohatxts of the 

 fowl; female, seen on the ventral surface; 

 magnified ISO diameters. 



