DISEASES OF HORSES 279 



The object of the tip is to throw the weight on the frog and 

 heels, which are readily spread after the horn has been cut away on 

 the sides of the wall. The internal structures of the foot at the heels, 

 being relieved of excessive pressure, regain their normal condition if 

 the disease is not of too long standing. The blister tends to relieve 

 any inflammation which may be present, and stimulates a rapid 

 growth of healthy horn, which, in most cases, ultimately forms a 

 wide and normal heel. In old, chronic cases, with a shrunken frog 

 and increased concavity of the sole, accompanied by excessive wasting 

 of all the internal tissues of the foot, satisfactory results can not be 

 expected and are rarely secured. Still, much relief, if not an entire 

 cure, may be effected oy these measures. 



SAND-CRACKS. 



A sand-crack is a fissure in the horn of the wall of the foot. These 

 fissures are quite narrow, and, as a general rule, they follow the direc- 

 tion of the horny fibers. They may occur on any part of the wall, 

 but ordinarily are only seen directly in front, when they are called 

 toe-cracks ; or on the lateral parts of the walls, when they are known 

 as quarter-cracks. 



Toe-cracks are most common in the hind feet, while quarter- 

 cracks nearly always affect the fore feet. The inside quarter is more 

 liable to the injury than the outside, for the reason that this quarter 

 is not only the thinner, but during locomotion receives a greater 

 part of the weight of the body. A sand-crack may be superficial, 

 involving only the outer parts of the wall, or it may be deep, involv- 

 ing the whole thickness of the wall and the soft tissues beneath. 

 The toe-crack is most likely to be complete that is, extending from 

 the coronary band to the sole while the quarter-crack is nearly al- 

 ways incomplete, at least when of comparatively recent origin. Sand- 

 cracks are most serious when they involve the coronary band in the 

 injury. They may be complicated at any time by hemorrhage, in- 

 flammation of the lamina, suppuration, gangrene of the lateral car- 

 tilage and of the extensor tendon, caries of the coffin bone, or the 

 growth of a horny tumor known as a keraphyllocele. 



Causes. Relative dryness of the horn is the principal predis- 

 posing cause of sand-cracks. Excessive dryness is perhaps not a 

 more prolific cause of cracks in the horn than alternate changes 

 from damp to dry. It is even claimed that these injuries are more 

 common in animals working on wet roads than those working on 

 roads that are rough and dry; at least these injuries are not common 

 in mountainous countries. Animals used to running at pasture when 

 transferred to stables with hard, dry floors are more liable to quarter- 

 cracks than those accustomed to stables. Small feet, with thick, hard 

 hoofs, and feet which are excessively large, are more susceptible to 

 sand-cracks than those of better proportion. A predisposition to 

 quarter-cracks exists in contracted feet, and in those where the too 

 turns out or the inside quarter turns under. 



Heavy shoes, large nails, and nails set too far back toward the 

 heels, together with such diseases as canker, quittor, grease and sup- 

 purative corns, must be included as occasional predisposing causes of 



