194 DISEASES OF POULTRY. 



head to that of a pea or a grain of corn. The largest 

 are found about the beak, the nostrils, the eyelids, 

 and upon other parts of the head that are free' from 

 feathers. They form rough, yellow masses upon the 

 comb and wattles. The eruption may be localized 

 where it first appears or it may extend to the feathered 

 portions of the body. 



With pigeons the eruption has a tendency to become 

 diffuse and invades the neck, the lower surface of the 

 body, the inner sides of the legs and wings, the rump 

 and even the upper surface of the wings. 



The nodules, which at first have somewhat the ap- 

 pearance of the warts offer seen upon the hands of 

 children, reach their full development in from five to 

 ten days. They soon show a central depression, an 

 opening forms, or the summit is rubbed off accident- 

 ally or by the bird's beak, after which there is a dis- 

 charge of a watery, or, later, of a thick, yellowish 

 matter which soils the feathers and which if abundant 

 may become foul and disagreeable. 



When the disease is localized, the general health of 

 the bird does not appear to suffer, and spontaneous 

 recovery may occur. In this case the nodules dry up 

 and form a crust which falls off either as a whole or 

 in particles. Generally, however, the disease extends, 

 the birds become emaciated, the plumage is rough, 

 the strength is exhausted, and death results. In the 

 most violent cases, especially with pigeons, the erup- 

 tion extends to the mucous membranes of the mouth 

 and nostrils, the resulting inflammation takes on a 

 diphtheritic form, and early death follows. 



Causation. — This disease has long been recog- 

 nized as contagious and to spread from one bird to 

 another. If an affected bird is introduced into a flock, 



