672 



DISEASES OF THE SKIN. 



orifice. Professor Hering has found in chronic grease large 

 numbers of acari, called sarcoptes Mppopodus, of which the 

 accompanying woodcut (Fig. 116) is an illustration. 



Hering says of it that its body is twice as long as broad, 

 beset all over with hairs like satin ; head retractile ; proboscis 

 consisting of two valves moving laterally ; mouth directed rather 

 downwards ; close to it two small palpi ; eight feet, five-jointed, 



the last joint as long as the four 

 preceding, with a small sucking disc 

 at the end, and two small hairs on 

 each joint. Two pairs of feet originate 

 near the head, and two posteriorly on 

 the belly. On the abdomen a small 

 prominence, and four long, straight, 

 plumose bristles; their length 0'16, 

 their breadth 0'08— 0-085"'. The 

 three pairs of bristles on the back 

 and those at the abdomen can be 

 raised like the tail of a peacock. The 

 large bristles are plumose ; the hairs 

 on the joints of the feet diminish in 

 length towards the extremity of the 

 foot. Only the third joint of the 

 first pair of feet has a longer hair. 



The presence of this parasite in 

 chronic grease is accidental; and 

 other diseases, such as canker, mal- 

 lenders, and sallenders, are apt to 

 become complicated with a mange' caused by this parasite. 

 Gerlach designates this epizoon symbiotes equi, and says that the 

 disease induced by it may be called foot-mange; but it has 

 nothing in common with canker, or other known cutaneous 

 eruption. Attention is at first drawn to a horse with this 

 disease by his rubbing his fore legs, or striking constantly with 

 the hind ones during the night. The seat of the disease, and 

 the ready detection of numerous parasites in clusters where the 

 crusts or scabs form, about the horse's heels, &c., suffice to enable 

 us to diagnose the malady. 



The swelling of the legs affected with grease, at first consisting 

 of material capable of reabsorption, becomes transformed, in 



Fig. 116. — Sarcoptes hippopo- 

 dus. — (Hering.) 



