NAVICULAR DISEASE. 379 
ease from injury. With regard to the first cause, it was recognized by 
the late W. Percival, one of Coleman’s most enthusiastic pupils; and, 
as concerns the last, its efficacy as a preventive needs no pleading nor 
any reference to establish its merits. 
The horse, when attacked, commonly has a good open foot—in fact, 
before disease commences, the foot is healthy. An animal in this con- 
dition is being ridden or slowly led out of the stable. In the last case 
it, being fresh, may rejoice to feel and sniff the cool air of heaven. It 
may prance about, and we may admire its attitudes; but in an instant 
it becomes dead lame. So a horse may be mounted by a kind master; 
the creature may be going its own pace, when, of a sudden, the move- 
ment shall change, and the rider will be made conscious that his steed is 
lame. 
In either case the foot is examined. It is cool, quite cool; no stone 
appears to have injured it—nor is any pebble sticking between the web 
of the shoe and the sole. Yet the lameness is acute and does not pass 
off. Now, to explain this, let the reader turn to the illustration which 
was last presented. 
The portion of the foot, immediately under the navicular bone, has 
been placed upon a stone; the stone has been forced against the foot by 
the immense weight of the horse imposed upon it. The stone, under 
this impulse, has bruised the navicular bone. But the fleshy frog and the 
perforans tendon would have to be passed before this effect could reach 
the bone. Are neither of these also hurt? Doubtless they are. But 
the fleshy frog is a highly organized, secretive organ, and probably, by 
its innate energy, soon recovers from the effect. The tendon is, on the 
contrary, too soft and yielding to retain any harsh impression. The 
bone is firm and solid; and thus that which failed to act upon either of 
the intervening parts, leaves a lasting injury upon the osseous structure, 
which, moreover, is held stationary by the coronary bone, and which is 
disposed to display injury, being covered by synovial membrane. 
The navicular bone belongs to a peculiar class called ‘“sesimoid, or 
floating bones.” These are more highly organized than the generality 
of osseous structures—in short, quite as much, or rather more, than the 
human tooth. Everybody must be acquainted with the anguish occa- 
sioned by unexpectedly biting upon a hard substance. The tooth, how- 
ever, is coated with crystalline enamel. The bone is covered by delicate 
synovial membrane. The impression is, therefore, more likely to be 
lasting with the last than the first. 
After the expiration of a week, however, the lameness disappears, and 
the proprietor fondly hopes all is over. The animal may work soundly 
for months—sometimes it never fails again. Generally, however, after 
