28 BULLETIN 487, TJ. S. DEPARTMENT OF AGRICULTURE. 
veloped by the cartilage changing to solid bone. They may cause 
lameness and pain, especially when the horse is driven on hard pave- 
ment. A fistulous abscess, known as quittor, may also occur upon the 
coronet. 
Feet. — Founder is indicated by rings and ridges around the hoof 
wall, an abnormal projection of the toe. and a convex sole. (The 
rings and ridges are close together at the toe and diverge toward the 
heel.) Founder also causes lameness. "Weak feet are subject to 
cracking. A crack in front of the foot is known as a sand crack, and 
those on the quarters are known as quarter cracks. Upon the soles 
of the feet there may be corns, or a diseased condition of the frog 
known as thrush. 
II o els. — It is very essential that the student knows the structural 
outline of a perfect hock, otherwise it will be difficult to detect cer- 
tain unsoundness common to this region. Thoroughpin is one of the 
troubles often difficult to detect. It consists of a soft swelling having 
its origin between the tendon and the bone, appearing just above the 
hock. 
There may be associated with thoroughpin a trouble known as bog 
spavin. This trouble is found in the depression that occurs on the 
inner forward part of the hock. It is caused by the oil from the 
joint accumulating and forming a soft swelling. Sometimes the term 
blood spavin is applied to these swellings and to an enlargement of 
the vein that passes the hock from the front. Xone of these troubles 
are considered unsoundness in a technical sense unless they are pro- 
ductive of lameness. Just under the hock at the rear the ligaments 
may thicken, forming a bulging calloused enlargement knoAvn as a 
curb. 
The worst trouble of the hocks and the most common is bone 
spavin. Xature in her attempt to strengthen a weak hock often 
causes a deposit of bone about the joint. Xeedless to state that this 
interferes with action, causing lameness. The lameness usually 
lessens with exercise. 
Stifle. — Be sure there are no swellings about the stifle. 
General unsoundness. — It is necessary to drive a horse hard for 
some distance to determine if his wind is sound. By stopping him 
quickly and listening in a position close to the neck it may be de- 
termined whether the breathing is natural. There may be a roaring 
or whistling sound indicating disorders of the air passages. Irregu- 
lar, spasmodic breathing indicates heaves, another unsoundness of 
the horse. 
Vices. — Such vices as kicking, balking, shying, and a tendency to 
run away are not met with in draft horses to the extent that they 
occur in lighter horses. Stable vices such as cribbing, weaving, tail 
rubbing, and halter pulling, as well as the vices mentioned above, 
