Diseases of the Skin 241 



water or some other source, under certain conditions. 

 Warm and wet weather seem to increase the virulency of the 

 virus and favor the rapid transmission of the disease. It is 

 not impossible that ants may have a role to play in the trans- 

 mission or cause of sore-head. 



"Pathological Anatomy. — On the skin the small, greasy- 

 like nodules, or hypertrophied nodules of the skin, contain 

 epithelial cells that have in them 'greasy' refractive bodies 

 that stain yellow with picro-carmine and the nuclei of the 

 epithelial cells become 'reddish brown' in color. Nearly all 

 the epithelial cells in the nodule appear larger than normal 

 and contain the refractive bodies. In the younger epithelial 

 cells these bodies (young coccidia) are relatively small and 

 occupy I to ^ of the epithelial cavity. In the older or 

 outer or cast-off epithelial cells these refractive bodies are 

 said by Freidberger and Frohner to occupy the entire cavities 

 of the epithelial cells. The invaded or infested epithelial 

 cells are unusually larger than the epidermal cells of the 

 healthy neighboring skin. Among the cast-off mass of 

 epithelial cells are found round refractive bodies and numer- 

 ous nuclei of leucocytes or pus cells. The subcutaneous con- 

 nective tissue is hyperaemic (congested) and is infiltrated with 

 cells (leucocytes and nuclei of disintegrated cells). Possibly 

 some of the small nuclei-like bodies among the cells in the sub- 

 cutis may represent one stage in the development of coccidia. 

 Many observers have, also, found various bacteria in the 

 nodule and subcutis. 



"When the exudate on the mucous surface or the crust of 

 the nodule of the skin is torn off the raw surface bleeds rather 

 freely and a fresh mount of this blood contains a short oval 

 bacillus, numerous round bodies usually said to be nuclei of 

 leucocytes ; and a few polynuclear leucocytes. Repeated 

 inoculations in the comb, wattles, skin and conjunctiva and 

 oral mucosa of healthy chickens of various ages, with this 



