DISEASES OF THE FETLOCK, ANKLE, AND FOOT. 433 



Fast work on hard roads, jumping, and blows on the coronet, 

 together with calk wounds of the feet, are accidental causes of quar- 

 ter cracks in particular. Toe cracks are more likely to be caused by 

 heavy pulling on slippery roads and pavements or on steep hills. 



Symptoms. — The fissure in the horn is of ttimes the only evidence 

 of the disease; even this may be accidentally or purposely hidden 

 from casual view by mud, ointments, tar, wax, putty, gutta-percha, 

 or by the long hairs of the coronet. 



Sand cracks sometimes commence on the internal face of the wall, 

 involving its whole thickness excepting a thin layer on the outer 

 surface. In these cases the existence of the injury may be suspected 

 from a slight depression, which begins near the coronary band and 

 follows the direction of the horny fibers; but the trouble can only be 

 positively diagnosed by paring away the outside layers of horn until 

 the fissure is exposed. In toe cracks the walls of the fissure are in 

 close apposition when the foot receives the weight of the body, but 

 when the foot is raised from the ground the fissure opens. In quar- 

 ter crack the opposition is true ; the fissure closes when the weight is 

 removed from the foot. As a rule, sand cracks begin at the coronary 

 band, and as they become older they not only extend downward, but 

 they also grow deeper. In old cases, particularly in toe cracks, the 

 horn on the borders of the fissure loses its vitality and scales off, 

 sometimes through the greater part of its thickness, leaving behind 

 a rough and irregular channel extending from the coronet to the 

 end of the toe. 



In many cases of -quarter crack, and in some cases of toe crack as 

 well, if the edges remain close together, with but little motion, the 

 fissure is dry ; but in other cases a thin, offensive discharge issues from 

 the crack and the ulcerated soft tissues, or a funguslike growth 

 protrudes from the narrow opening. 



When the cracks are deep and the motion of their edges consider- 

 able, so that the soft tissues are bruised and pinched with every 

 movement, a constant inflammation of the parts is maintained and 

 the lameness is severe. 



Ordinarily the lameness of sand crack isi slight when the patient 

 walks, but it is greatly aggravated when he is made to trot, and the 

 harder the road the worse he limps. Furthermore, the lameness is 

 greater going downhill than up, for the reason that these conditions 

 are favorable to an increased motion in the edges of the fissure. 

 Lastly, more or less hemorrhage accompanies the inception of a sand 

 crack when the whole thickness of the wall is involved. Subsequent 

 hemorrhages may also take place from fast work, jumping, or a 

 misstep. 



36444°— 16 ^28 



