170 VETERINARY MEDICINE AND SURGERY. 



their action is torpid, the sebaceous matter is concreted into a solid 

 form, and distends the excretory duct and hair follicle even to the ori- 

 fice. Professor Hering has found in chronic grease large numbers of 

 acari, called Sarcopfes hippojjodiis, of which the accompanying woodcut 

 (Fig. 81) 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 downward; close to it 

 two smiill 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 O.IG, their breadth 0,08- 

 0.085 lines. Tiie 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 to- 

 ward the extremity of the foot. Only the third Joint of the first -^air of 

 feet has a longer hair. 



The presence of this parasite in chronic grease is accidental ; and 

 other diseases, such as canker, mallenders, and sallenders, are apt to be- 

 come complicated with a mange caused by this parasite. Gerlach desig- 

 nates this epizoon SymUotes 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. 



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

 material capable of reabsorption, becomes transformed, in neglected 

 cases, into a low form of fibrous tissue, constituting what is termed 

 elephantiasis; in some cases the affected limbs become enormously en- 

 larged from this cause. 



Etiology. — The exciting causes of grease are, improper food, espe- 

 cially moist, inferior, and cooked food, clipping the hair of the heols and 

 legs, filth, and neglect. 



Grease may also arise from a cut or bruise of the skin of the heel ; 

 but as a general rule it is then due to neglect of the wound rather than 

 to the original injury. Occasionally grease arises from a plethoric condi- 

 tion combined with want of i^roper exercise. 



In some instances the best bred and best cared for horses are liable to 

 grease; but in them it scarcely ever assumes a chronic character, but par- 



