NAVICULAR DISEASE. 
477 
Such are the means provided for dispelling the shock to the 
joints and vertical bones, and ample as they seem to appear they, 
nevertheless, fail to relieve the parts from concussion and exces¬ 
sive pressure of the sensitive structure within the hoof, due to 
rapid pounding over hard surfaces. 
Hence there arises a bruise of the navicular bone, the bursa 
in connection therewith and the perforans tendon, and the 
disease is chiefly found in those animals that are high knee 
actors or rapid pace makers. 
Professors Smith and Paw differ as to the class of horses 
among which it is most commonly found. 
Smith says, “It is rare in racing, hunting, and even in trot¬ 
ting horses, so long as they are used on the turf.” 
Law says, “ The thoroughbred is more commonly affected 
with the disease than any other.” 
But the fact is that beside the exciting causes, must be con¬ 
sidered the predisposition in individual animals, most prominent 
among which are heredity, and vice of conformation, and added 
to this the environments of domestication and use, such as dry 
stables, i. e., board floors in stables, hard and fast work, bad 
shoeing, and puncture wounds. 
Mr. Turner writes : “ Contraction mostly takes place in ani¬ 
mals that have been accustomed to be shod before the age at 
which they have attained their highest value for work, viz., five 
years, but this contraction is not, however, necessarily connected 
with lameness. The next deviation from nature is the passive 
state to which the foot is subjected for 24 hours, and sometimes 
several days. Compare this with the few hours during which a 
horse in a state of nature, that is, roaming at will in the pasture 
field, is in a quiescent condition, and there will be no cause of 
surprise in the change of form, position, character and the state 
of contraction which takes place in the foot deprived of its 
natural pressure and motion. The first consequence of contrac¬ 
tion is the gradual displacement of the os navicular and os pedis 
bones ; they ascend within the hoof, and an unnatural arch is 
formed by the ascent of the frog. The delicate synovial mem- 
