230 THE DISEASES OF THE DOG. 



parasites, we shall have to note those organisms of the 

 vegetable kingdom which have clinical importance as 

 giving rise to ringworm and favus. 



Animal Paeasites of the Skin (Dermatozoa) and the 

 Disorders to which they give rise. — These disorders are 

 essentially inflammations of the skin, a fact which must be 

 constantly kept in mind in dealing with them practically. 

 Although they are due to the parasite, and essentially 

 depend on its presence and activity, it cannot be doubted 

 that certain states of the constitution and defects in hygiene 

 predispose to the various forms of mange. So much is this 

 the case that mange has been considered hereditary. It has 

 been remarked that animals confined in close kennels sub- 

 jected to the acrid effluvia from urine and other evacuations ; 

 those fed high and little exercised ; ill cared for, starving 

 brutes ; those dogs kept on beds of barley straw, and fed with 

 too much meat, bad flesh, or constant salt food are very 

 liable to suffer. Contagion is, however, the active producer 

 of the disorder ; the parasites, as a fixed contagium, are 

 transmitted by direct or indirect contact from the affected 

 to the healthy. Some forms of animal parasitic diseases are 

 more contagious than others owing to the habits of the 

 organisms which give rise to them, but we have no evidence 

 of these disorders being infectious, although the vegetable 

 parasitic disorders are possibly so. 



True Mange of the dog is technically known as Sarcoptic 

 Scabies, as being similar to " itch " of man, and " scab " 

 of sheep, and due to Sarcoptes canis. This parasite gene- 

 rally invades the skin, of the back and neck, from thence 

 gradually extending to other parts of the body, and in- 

 ducing local disorders, when it invades the eyelids, ears, 

 and feet. Fleming describes it as first affecting the 

 face. It causes by its ravages much irritation, so that 

 some fever is often present at first. The patient's appe- 

 tite is generally good, but he becomes very thin from the 

 amount of irritation constantly produced by the parasite. 

 This irritation occurs especially when the skin is excited 

 by warmth or suddenly after eating or drinking. The 

 dog bites and scratches himself constantly and when 



