CHAPTER XVII. 



Diseases oe the Skin. 

 Pavus {Baldness or White Comb). 



This disease of the skin attacks poultry as well as man and 

 the domestic mammalia. In mammals it is called tinea favosa or 

 favus. 



Diagnosis. The disease usually appears first as small gray 

 white spots on the comb, wattles, eye lids and around the ears, 

 that is, on the unfeathered parts of the head. The spots enlarge 

 and run together forming a scaly crust which becomes thicker 

 until in 3 or 4 weeks it may be as much as 8 millimeters (1-3 

 inch) thick. The scales which make up the crust are often 

 formed in concentric rings, the margins raised and the centers 

 depressed, so that the scale is somewhat cup shaped. When the 

 crust is removed the skin appears irritated and in places the sur- 

 face is somewhat raw. The disease spreads to the feathered 

 parts of the head, the neck, and the region around the vent. 

 The base of the feathers becomes 

 surrounded by concentric rings of 

 the scaly material. The feathers 

 become dry, erect, and brittle and 

 finally break off or fall out leaving 

 a disc-shaped scale with a depres- 

 sion at the bottom where the base 

 of the feather was located. The 

 bird's head and neck and patches 

 around the vent become bare of 

 feathers. The exposed skin is cov- ''.^/j^^y-'-']'^',i^-- 

 ered with the cup-shaped scales. i^i^^if\0i^$f4} 

 Sometimes the disease spreads over ''■^»- ''■''■'"''*'"■' ^' 

 the whole body until the bird be- 

 comes nearly naked. The diseased 

 bird has a peculiar disagreeable 

 odor, sometimes likened to the odor 

 of a musty grain or to mouldy 



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Fig. 37. Head and neck of 

 a fowl . affected with gen- 

 eralized favus. (After 

 Pearson). 



