405 



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 blis- 

 ter not onl}^ tends to relieve any inflammation which may be present, 

 but it also 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, of course 

 satisfactory results can not be expected and are rarel}^ secured. Still 

 mnch relief, if not an entire cure, maj' be effected by these measures. 

 When thrush is present as a complication its cure must be sought 

 by such measures as are directed in a consideration of this disease 

 under its proper heading. If sidebones, ringbones, navicular disease, 

 contracted tendons, or other diseases have been the cause of con- 

 tracted heels, of course treatment of the result will be useless until 

 the cause is removed. 



SAND-CRACKS. 



A sand-crack is a solution of continuity or fissure in tlie horn of the 

 wall of the foot. These fissures are quite narrow, and as a general 

 rule they follow the direction of the liornj^ fibers. They may happen 

 on any part of the wall, but ordinarilj^ they are only seen directly in 

 front, when they are called foe-cracks; and on the lateral parts of the 

 walls, when thej^ are known as quarter-cracks. (Plate XXXIII.) 



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

 nearly alwaj'S affect the fore feet. The inside quarter is more liable 

 to the injury than the outside one, 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, involving the 

 whole thickness of the wall and the soft tissues beneath. 



Tlie toe-crack is most likely to be complete — that is extending from 

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

 always incomplete, at least when of comparatively recent origin. 

 Sand-cracks are most serious Avhen they involve the coronary band in 

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

 inflammation of the lamina^, suiipuration, gangrene of the lateral 

 cartilage 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 i)redisposing 

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

 lific cause of cracks in the horn than alternate changes from damp to 

 dry. It is even claimed that these injuries are more common in ani- 

 mals working on wet roads than in those working on roads that are 

 rough and dry; at least these injuries are not common in mountain- 

 ous countries. Animals used to running at i)asture Avhen ti-ansferred 



