DISKASKS OF POULTRY. 



185 



crushed into powder. A micrcscopic examination of 

 this powder reveals numerous mites and the del)ris 

 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 

 readily co m ni 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 

 bj' copulation, and 

 spreads rapidly to the 

 back, the thighs and 

 the belly. An infest- 

 ed cock will rapidly 

 infect all the fowls in 

 a poultr3'-3'ard. Often fij,'. *'i.—Ef-hi,r»!optis bUotuiius of the 



, ^ fowl; female, seen on the ventral surface; 



the head and the up- magnilieil ISJ diameters. 



per surface of the neck are 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 



