432 DISEASES OF THE HORSE. 



TV^ien thrush is present as a complication, its cure must be sought 

 b}^ measures directed under that heading. If sidebones, ringbones, 

 naAdcuhir disease, contracted tendons, or other diseases have been the 

 cause of contracted heels, treatment will be useless until the cause is 

 removed. 



SAND CRACKS. 



A sand crank 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 di- 

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

 but ordinaril}^ are onl}^ seen directly in front, when the}'^ are called 

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

 as quarter cracks. (Plate XXXVI.) 



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 gi'eater 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. 



The toe crack is most likely to be complete — ^tliat is, extending from 

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

 ways incomplete, at least Avhen of comparatively recent origin. Sand 

 cracks are most serious when they involve the coronarj' band in the 

 injury. They may be complicated at an}'^ time by hemorrhage, in- 

 flammation of the laminae, 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 predispos- 

 ing 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 Avorking on roads that 

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

 tainous countries. Animals used to running at pasture when trans- 

 ferred to stables with hard, dry floors are more liable to quarter 

 cracks than those accustomed to stables. Small feet, Avith 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 Avhere the toe 

 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 sand cracks. 



