594 ACUTE INFECTIOUS DISEASES 



sary, as is shown by the spread of the disease at poultry 

 shows. A bird with mucous membrane lesions may trans- 

 mit the disease to a susceptible bird in the cutaneous form, 

 and vice versa. 



Emulsions of scrapings from either cutaneous or mucous 

 membrane lesions injected subcutaneously, submucously or 

 applied to scarified areas on the skin, would in some cases 

 produce the generalized form of the disease. Similar results 

 were produced by using an emulsion of a twenty-four-hour 

 agar growth of cultures taken from lesions and injected 

 subcutaneously. 



It is possible at times by scarifying the mucous mem- 

 brane of apparently healthy birds to produce at the point 

 of injury local lesions not unlike those of this disease, but 

 they disappear in a few days without manifestation of 

 general symptoms. Incomplete experiments by using the 

 blood of sick birds in an attempt to produce the disease 

 gave negative results, which is contrary to that claimed by 

 a few other investigators. 



Natural Infection. —There are a variety of ways by which 

 natural infection takes place. Cohabitation is one of the 

 most common, an infected bird introducing the disease 

 into an entire flock. The exfoliated membranes, or the 

 exudate given off while sneezing or coughing, act as inter- 

 mediary carriers to the healthy birds. The infection in this 

 way will find lodgment on the skin where there are slight 

 abrasions, or on the mucosa of the eyes or mouth, where 

 it develops either to form the pox lesions or the various 

 other forms found on the mucous membranes. 



It is quite possible to have the disease develop in the 

 eyes by the infection gaining entrance, and the bird irri- 

 tating the skin and conjunctiva by rubbing them against 

 objects or by scratching them with their feet. The disease 

 is frequently spread by food or drink which is contaminated 

 with infective material. 



A very common source of the disease is the poultry show 

 where infected birds are exhibited, and conditions exist 

 favorable to reduce the bird's resistance. It very fre- 

 quently happens that on the return of birds from the show 



