458 Veterinary Medicine. 



2ist. Neurosis. These may be exemplified by the intense 

 itching of the skin without appreciable structural change. So in 

 cutaneous anaesthesia and hyper sethesia. 



22d. Modified Secretions. These include absence of per- 

 spiration — anidrosis, excessive perspiration— hyperidrosis, sup- 

 pressed sebaceous secretion — asteatosis, excessive sebaceous secre- 

 tion — steatorrhea or seborrhea, foetid sweat — bromidrosis, colored 

 sweat — chromidrosis, urinous sweat — uridrosis. 



23d. Structural alterations in glands and ducts. Cystic 

 ducts — hydrocystoma, blocked ducts — acne, inflamed glands — 

 hidrosadenitis. 



24th. Abnormal conditions of the hair. This embraces 

 baldness, hypotrichosis, alopecia, excessive growth of hair, 

 hypertrichosis, white patches, canities, nodular hairs, piedra, 

 brittle hair, fragilitas crinium, felted hair, plica, trichoma. 



25th. Scleroderma. Hard, leathery, thickened skin. Exam- 

 ples in old boars on shoulders, and in other animals. 



26th. Elephantiasis Pachydermia. Enormous hypertrophy 

 of the skin, with usually distention of the lymph plexuses and 

 vessels (lymphangiectasis : see Vol. \). 



27th. Vegetable parasites. Trichophyton, achorion, mi- 

 crosporon, actinomyces, etc. (See parasites). 



28th. Animal parasites. lyice, fleas, diptera, trombidium, 

 Acari, Ixodes, cimex, filaria, coccidia, etc. (See parasites). 



GENERAI, CAUSES OF SKIN DISEASES. 



External Internal. Traumas, abrasions, excoriations, lacerations, con- 

 tusions. Compression, radiating heat, scalding, incandescent objects, solar 

 heat, chemical caustics, cold, freezing, kicks, bites, tusk, horn or claw 

 wounds, Slings, venoms, envenomed bites, road dust, sweat, excretions,, 

 sebum, mineral and vegetable poisons, essential oils, fungi. Hypersemia, 

 exudation, depilation, sudation, moulting, climatic changes, unwholesome 

 or irritating foods, ptomaines, alimentary fermentations, hepatic, renal or 

 blood disorders, altered innervation, youth, age, temperament, heredity. 

 Experimental nervous cases. 



These may be external or internal or both. 



External Causes. Some affections of the skin are due to 



