EPITHELIOSIS INFECTIOSA AVIUM 595 



the disease develops in the course of a week or ten days. 

 Sparrows and pigeons are common carriers, often trans- 

 porting the infection great distances. This is a very impor- 

 tant method of transmission often overlooked. The disease 

 has been observed in sparrows in a number of cases and 

 exhibiting in them the same characteristics as in other 

 birds. Sparrows and pigeons come in direct contact with 

 poultry at feeding time and thus infect them. It is some- 

 times spread by such intermediary agents as infected coops, 

 clothing, etc. Young birds are more susceptible to the 

 infection than older ones. Pigeons and chickens seem to 

 be far more susceptible than other birds. 



It has been observed that one attack of the disease will 

 produce immunity for a certain period. Either the skin 

 form or involvement of the mucous membranes confers 

 equal immunity against the opposite form. 



Pathology.— The postmortem findings vary with the 

 immediate cause of death. In rare cases when death is 

 due to suffocation early in the disease only the acute con- 

 ditions are noted. The body appears fairly well nourished, 

 the mucous membranes are covered with a thick slimy 

 mucus which may occlude the upper air passages. In the 

 larynx, or somewhere along the trachea, possibly in the 

 larger bronchi, will be found the mass of dense, tough, 

 yellowish material obstructing the lumen. 



In some cases when both eyes are involved death results 

 from starvation early in the disease. The body is emaciated. 

 The mucous membranes of the eyes, and often of the mouth 

 and respiratory passages show inflammation, and usually 

 there is a mass of this same yellow material in the con- 

 junctival sac distorting or obscuring the eyes. The skin 

 around the eyelids may also be involved. 



The majority of the fatal cases die in two to five weeks. 

 In these the body shows all the symptoms of a toxemia, 

 emaciation is pronounced, and the serous membranes 

 studded with petechia?. In the cutaneous form the skin 

 presents all the symptoms of a severe inflammation, each 

 nodule being a distinct process. Some of them show a 

 similarity to tumor formation, especially on the comb where 



