DISEASES WHICH ARE INDUCED BY PARTICULAR PARASITES 167 



common mange and the other a burrowing mite [Sarcoptes) the ravages of 

 which induce a more severe kind of skin disease, which is difficult to cure 

 owing to the mites burying tliemselves under the cuticle. 



Symptoms. — In all forms of mange the prominent symptom in the 

 first instance is itching, which induces the animal to bite and rub itself, 

 sometimes so vigorously as to cause abrasion of the skin. The disease 

 is first apparent on the withers, the upper part of the neck, the root of the 

 mane. Ultimately it may reach the head, and indeed most parts of the 

 body excepting the extremities. An examination of the skin will lead 

 to the detection of small pimples, and elevations of the cuticle from the 

 exudation which goes on beneath it. The formation of scabs all over the 

 affected surface follows, and these become confluent as the disease advances. 

 Scabs, if violently removed, disclose a raw surface beneath. 



A peculiar form of mange in the extremities, due to the presence of 

 a variety of mange-mite, which is known as the Syiiihiotes on account 

 of l)eing found in clusters or colonies, occurs in the horse, but is only rarely 

 detected, as the itching which induces the animal to rub and l)ite its legs 

 is generally ascribed to other causes. The acarus usually locates itself in 

 the hind fetlocks, but occasionally it attacks all four limljs, and it is 

 commonly found in cases of grease. The symbiotes appear to be par- 

 ticularly active at night, and a knowledge of this fact is important, because 

 when a horse is found to kick at the stall-post or strike his hind- or fore- 

 feet constantly on the floor of the stable during the night, there is reason 

 to suspect the presence of this form of mange (symbiotic mange), and a 

 careful examination of the extremities should be made. The discovery of 

 the symbiotes in the loosened cuticle of the legs will furnish satisfactory 

 evidence of the nature of the disease. 



The varieties of mange are to be distinguished with absolute certainty 

 only by microscopic examination of the hair and scal)s taken from the parts 

 of the skin which are most affected. The examination is comparatively 

 easy. Scrapings from the diseased parts have to be placed in a drop of 

 water on the slide, teased out with dissecting needles, and covered in the 

 usual Avay with a thin covering glass, and examined with the half-inch 

 objective. The three varieties of mange-mites which have been mentioned 

 are illustrated in the accompanying plate (Plate XXXVI, figs. 5, 6, 7, 8), 

 and there will be no difficulty in distinguishing them by comparing them 

 under the microscope with the figures. 



Treatment. — Under ordinary circumstances mange in the horse is 

 amenable to treatment, but when sarcoptic mange is allowed to run its 

 course, the rapid multiplication of the parasites, and the damage which 

 they do to the skin, and the consequent irritation which results, frequently 



