ALOPECIA 465 



containing arsenic for its action on the skin. The external 

 treatment consists in cleaning applications with alkaline 

 solution (sodium carbonate, 2 per cent.) and applications 

 of salicylic ointment (10 per cent.). A solution of resorcin 

 (5 per cent.) is very satisfactory as it does not soil the 

 hair coat, nor cause dirt to adhere to it. It is best to clip 

 the hair and brush the skin well before medicinal treatment 

 is begun, and thereafter at frequent intervals. 



ALOPECIA. 



Definition.— A loss of hair, feathers or fur from large 

 or small areas due to causes other than organic diseases or 

 parasites. 



Etiology.— Mechanical.— Fowls, especially the males when 

 penned, may pluck the feathers from the breast, denuding 

 a large area. Female rabbits pull out their fur for use in 

 preparing a nest for their young. 



Chemical. — Acids or strong caustics by deep action on the 

 skin will destroy the hair follicles and when healing occurs 

 the area is free of hair. 



Thermic. — Hot water, often intentionally applied, may 

 act deeply enough to destroy the follicles and denude an 

 area. Burns appear similar but more diffuse. 



The most common cause is deranged nutrition to such 

 an extent that the hair falls out usually in patches over the 

 body. A single area, so affected, and when the usual 

 etiological factors are wanting, must be ascribed to a dis- 

 turbance of the trophic skin nerves of that part. In one 

 case the hair was lost each succeeding summer from pig- 

 mented parts of the skin. No cause could be given. 



Pathology.— The hair appears to loosen in patches and fall 

 out. The skin appears almost normal in some cases but 

 usually somewhat dry and hard. In those cases following 

 severe wounds, scalds, or burns, the skin shows scar forma- 

 tion. The microscopic examination for parasites is negative. 



Symptoms.— There appear on the skin small areas de- 

 nuded of hair, which gradually become larger. The hair 



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