172 Veterinary Medicine. 



two central leaf-like processes. Symptoms: Itching heel and fetlock in 

 hind limbs ; exceptionally to hocks and thighs. Patving, kicking, scratch- 

 ing, biting, especially at night and in winter, and in hairy-legged cart breeds. 

 Bristling, depilation, scurf, scab, papules, cracks, excoriation, sores, pro- 

 fuse foetid discharge, stocking, presence of acarus on surface. May be 

 months ere it passes to the horse alongside. Treatment : Simple, clip, 

 soapy wash, and inunction ; wash off and apply acaricide, tobacco, tar water, 

 sulphur, potassium sulphide. Prevention : As for sarcoptes. Symbiotes 

 lives 50 days in stable. 



Acarus. The Symbiotes Communis Var. Equi (S. Spathi- 

 ferus, Megnin ; Dermatophagus Equi) is much smaller than 

 the p.soroptes, the ovigerous female being .36 to .40 mm. long, 

 and the mature male .28 to .32 mm. The rostrum is only a little 

 longer than broad ; the two front pairs of limbs are very long and 

 thick, the third pair large, and the fourth short and thin. There 

 are no suckers on the third pair of limbs in the female. Behind 

 its two copulatory suckers, and on the posterior margin of the 

 body, the male has two prominent, retangular lobes, each bearing 

 two bristles and, centrally, two long, flattened, foliaceous pro- 

 cesses or spathes. 



Symptoms. The disease is characterised by its location on 

 the pastern, hollow of the heel and fetlock, mainly of the hind 

 limbs, from which when crowded the acari extend upward to the 

 hocks, exceptionally to the legs and thighs and still more rarely 

 to the croup, abdomen and loins. The first indications are an 

 incessant pawing or kicking of the ground, or scratching of one 

 pastern with the other foot. The patient may kick straight out, 

 or turn and attempt to bite the affected pastern. The itching is 

 u-sually greatest at night and in winter or when the horse stands 

 idle in the stable. Shoeing is often difficult owing to the horse 

 trying to rub his foot againist the operator. The disease is much 

 more common in heavy cart breeds, as imported Belgians, Suf- 

 folks, Shires or Clydes, in which the long and abundant hair 

 gives better cover for the parasite and stands in the way of 

 thorough cleanliness. The same breeds born in America part with 

 their long hair and are in some degree immune. Examination of 

 the affected part shows a bristling and loss of hair, an accum- 

 mulation of scurf and scabs, with an eruption of papules and the 

 formation of cracks, excoriations and extensive sores, and a free 

 unctuous, foetid discharge. Even at an early stage the hair is 



