The worst specimen of the affection the author has encountered, was in a horse which had been turned into a moist straw-yard and neglected. The thrush generally witnessed in the hind feet may be present in all four; but the writer knows of no instance in which the thrush peculiar to the fore feet was also observed in the posterior limbs.
Thrush does not generally provoke lameness. In its more aggravated forms, however, it interferes with the pace; and the horse having only incipient thrush is liable to drop suddenly, if the foot be accidentally placed upon a rolling stone. Now, knowing our roads are made of stones, and that the bottom of the horse's foot is, in the ordinary manner of shoeing, entirely unprotected, it is curious to state that this disease is commonly not esteemed unsoundness. Any thrush, when present, may lead to acute lameness; then the lameness would be unsoundness; if thrush simply interferes with the action, although it endanger the safety of the rider, it is, by the code of veterinary legislation, esteemed no reasonable objection to the soundness of a horse. In the author's opinion, any animal should be esteemed unsound which has suffered from loss of or from change of any structure that ought to be present, or has any affection which reasonably could subject it to remedial treatment.
OSSIFIED CARTILAGES.
This signifies a conversion into osseous structure of the cartilages naturally developed upon the wings of the coffin-bone, or the bone of the foot. Here is a drawing of the largest specimen of this transformation which the writer ever witnessed. This was borrowed from the museum of T. W. Gowing, Esq.; and, from the magnitude of the disease, the writer should imagine the posterior of the pastern must have been in the living animal somewhat deformed.
OSSIFIED CARTILAGES.
The lateral cartilages of the horse's foot have
undergone change and become bone; being
now continuous with the os pedis.
In heavy horses, working upon London stones, so certain are the cartilages to become ossified that several large firms pay no attention to this defect. They prefer an animal with a confirmed disease to a sound horse, which will be certain to be ill during the change, and the extent of whose subsequent alteration no one can predicate. So far these purchasers act wisely; but, in horses designed for fast work, ossified cartilages are a serious defect. They frequently occasion lameness, and always interfere with the pleasantness of the rider's seat. When accompanied by ring-bone, ossified cartilages give rise to the most acute and irremediable lameness.
Ossified cartilages are incurable. No drugs can force Nature to restore the original structure which has been destroyed. Once let a cartilage become ossified, and it remains in that condition for the creature's life. There is little difficulty in ascertaining when this change has taken place. The hand grasps the foot just above the coronet; the fingers are on one side, and the thumb upon the other. The cartilages lie at this place, immediately under the skin. Cartilage is soft, pliable, and semi-elastic. It yields very readily to pressure. However, when the thumb and fingers forcibly press the part, if, instead of feeling the substance under them yield, the hand is sensible only of something as hard as stone, or any way approaching to such a character, that is proof positive the cartilages are ossified, or are approaching change. If the horse has recently gone lame, and the seat of cartilages feels of a mixed nature—partly soft and partly hard—apply a blister to the coronet, so as to convert that which is a subacute process into an acute action, and with the cessation of activity hope to stop the deposit. Repeat the blister if absolutely necessary; but there is no occasion to subject more than the coronet, and a couple of inches above that structure, to the operation of the vesicatory. Indeed, blisters act more effectually upon confined spaces. This is all that can be accomplished, save by good feeding and liberal usage: these are essential, because every abnormal change denotes a deranged system; and this is, in the animal, soonest mended by generous diet. Perfect rest and two pots of stout per day may even be allowed, should the pulse be at all feeble.
