A HORSE, WITH NAVICULAR DISEASE, POINTING IN THE STABLE.
The effect of these repeated attacks is soon shown. The anguish has been likened to toothache, only it must assuredly be a toothache twenty times magnified. All people know "there never yet was philosopher who could withstand the toothache;" but think of the poor horse with twenty toothaches compressed into one agony! The man can seek a thousand changes to divert his suffering; the simple horse cannot even drink intoxicating fluids, and has hitherto not learned to smoke. The suffering, therefore, continues. And as man strives to spare a decayed tooth by masticating on the other side of the mouth, the horse endeavors to ease an aching foot by leaning all its weight upon a sound limb. Thus it learns to point in the stable or to advance one leg beyond the center of gravity, leaving the healthy member to support the entire weight of the body.
THE UPRIGHT PASTERN AND HARD, UNYIELDING HOOF, INDICATIVE OF CONFIRMED NAVICULAR DISEASE.
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; the crust becomes marked by rims and grows considerably higher. In fact, the foot, from being an open, healthy foot, becomes a strong, contracted, or diseased member.
THE TROT, PECULIAR TO NAVICULAR DISEASE, GENERALLY TERMED GROGGINESS.
The effect of the disease is speedily shown by the animal progressing 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 this stage, the mode of progression is usually what is termed groggy—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 "patter, patter! clatter, clatter!" which it makes.