NAVICULAR DISEASE. 381 
A foot thrown out of use decreases in size. Nature has given certain 
parts for certain purposes; and if these purposes are avoided, those 
parts diminish in bulk. Wear the arm in a sling 
for any extended period, and the arm will sensibly 
grow smaller, or become withered. So the horse’s 
foot, spared in progression and pointed in the 
stable, obviously changes its shape. The quarters 
draw inward; the heels narrow; the frog hardens 
and decreases; the sole thickens and heightens; gy. yernr pasrern AND 
the crust becomes marked by rims and grows con-  fAnh, UATenPine Boe 
siderably higher. In fact, the foot, from Deing — AYICUNAR DISEASE. 
an open, healthy foot, becomes a strong, contracted, or diseased member. 
The effect of the disease is speedily shown by the animal progress- 
ing entirely upon the toe, whereby the front of the shoe becomes much 
worn, as shown in the following engraving. Indeed, it is not unusual to 
see shoes taken from horses having navicular disease with their front 
edges worn positively to a cutting sharpness. When the animal is in 
THE TROT, PECULIAR TO NAVICULAR DISEASE, GENERALLY TERMED GROGGINESS. 
this stage, the mode of progression is usually what is termed grogey— 
that is, the hind feet, which are never affected, step out as boldly as 
ever; but the fore feet are limited in their action, They cannot be 
advanced far, because extension causes the perforans tendon to press 
upon the navicular bone; the leg cannot be bent, because flexion moves 
the perforans tendon upon the navicular bone. The animal, thus doubly 
disabled, endeavors to make up by quickened movement for that which 
it lacks in perfect action. It dare not bring the heel to the ground or 
take long steps. It therefore progresses upon the toes, and indulges in 
very short but quick movements of the fore feet; and a horse thus 
affected may be challenged, though unseen, by the “pater, patter! clat- 
ter, clatter!” which it makes. 
