378 NAVICULAR DISEASE. 
the perforans tendon, which is inserted into the inferior surface of the 
coffin-bone. A synovial sac is placed between the navicular bone and 
superior surface of the tendon, on which the ossoeus structure reposes. 
Synovial sacs are only found in places where motion is great and almost 
incessant; thus the existence of this formation apprises us that the bone 
and tendon, in a healthy state, are designed to move freely upon each 
other. They do this while unaffected by dis- 
ease; the foot, indeed, cannot be flexed, ex- 
tended, retracted, or placed upon the ground 
without this busy little joint being put into 
motion. It is, perhaps, as essential a part— 
though of small size—as any of the larger 
structures which enter into the horse’s body. 
ga cece es anata Navicular disease, however, affects only the 
a. The perforans tendon running lower surface of the bone; the upper surface 
beneath the bone, and on 
pubic tire oneitcposes: shares another synovial sac, which lubricates 
b. The comparative size and rela- 
he era the articulation of the coffin-bone with the 
oy ae eee ee lower bone of the pastern. This upper surface 
ot eionidens Sue ee is never affected; the navicular bone may di- 
lar disease is alone exhibited. minish or wither through disease, still the affec- 
tion remains confined to its original situation ; 
disease may lead to fracture of the bone or to rupture of the perforans 
tendon, still the superior portion of the navicular bone to the last 
exhibits a healthful condition. 
This most annoying and terrible disorder springs from two causes. 
The first was a very favorite crotchet of the late Professor Coleman, who 
was always theorizing to the injury of the animal it was his office to 
cure. The disease is now largely distributed through that gentleman’s 
favorite maxim concerning the absolute necessity that there should be 
pressure upon the frog. Every smith thus instructed tried to bring the 
frog as near the ground as possible, and the consequence was the spread 
of navicular disease. It is true, the frog, in a state of nature, was de- 
signed to hear pressure; but surely it is folly to talk about the natural 
condition of the horse when nothing like a wild horse exists. Here was 
Coleman’s error; he legislated for the most artificial of living creatures, 
which consumes only prepared food, and which moves only over labori- 
ously manufactured roads, as if it had been in an undomesticated con- 
dition, gamboling upon the untilled earth. 
The second cause is, the parsimony of most horse proprietors. Would 
these gentlemen have their favorites shod with leather, the smith would 
be obliged to slightly raise the frog; while the leather—if good, stout, 
3) 
sole leather—and the stopping would protect the seat of navicular dis- 
