554 



DISEASES OF THE SKIN. 



which have been observed during certain seasons in intermittent 

 acariasis must not be looked upon as cures. When mange is general- 

 ized the alterations of the skin are usually accompanied by general 

 symptoms : a permanent excitement and a persistent cutaneous 

 exudation delay the growth of young animals, disturb nutrition, 

 and in some cases lead to death through exhaustion and cachexia. 



Diagnosis. We possess facts and symptoms which permit us 

 to make a diagnosis of mange, besides the detection of parasites. 

 The enzootic character of the trouble, its contagiousness, its ap- 

 pearance in herds and rapid extension through their distribution are 

 important clinical peculiarities ; on the other hand, pruritus is 

 much more intense than in other dermatoses. The knowledge of 

 the selected places of the different manges is valuable from a 

 diagnostic standpoint. In the horse, the localization upon the 

 head (often followed by generalization) indicates sarcoptic mange ; 

 the eruption which is exclusively located upon the legs and tail is 

 characteristic of symbiotic mange ; the location of this affection 

 upon regions which are protected by mane or tail announces 

 psoroptic mange. 



But the safest diagnosis is the microscopic search for acari. 

 We make it by collecting the scabs in a dilute solution of 10 per 

 cent, of potash and examining them by means of a low power. In 

 sarcoptic mange of the dog it is necessary to scrape the skin deeply, 

 in order to find the parasites in the product thus obtained ; it may 

 be scraped with a sharp bistoury or we may make thin cuts into it 

 with a razor or scissors. Gerlach has recommended to apply sus- 

 pected scabs on a man's arm ; in the case of sarcoptic mange, 

 pruritus and a slight dermatitis is produced (?) after twelve hours, 

 and in case of psoroptic mange after two hours. For psoroptes 

 and symbiotes it is sometimes sufficient to place the suspected 

 scabs on black paper or in a case having a glass cover, and to ex- 

 pose them to a mild heat or to the sun. Soon we can see, with the 

 magnifying glass or with the naked eye, acari coming out of the 

 scabs and advancing on the surface of the paper or the glass. (For 

 differential diagnosis see the articles devoted to special manges.) 



Prognosis. It varies with the species of the parasite and the 

 degree of extension of the disease. 



Generalized sarcoptic mange of the horse is, so to speak, in- 

 curable; on the other hand, that of the pastern heals in a few 

 days. Generalized psoroptic mange of the sheep is very difficult 



