animated machine than a pea would cover, or the decayed part of a hollow tooth would exhibit. This destructive malady has, on a late occasion, been emphatically expressed, "The curse upon good horseflesh."

I have dissected all the groggy feet that I have been able to collect, and have found the navicular joint diseased in every instance.

DESCRIPTION OF THE DISEASED JOINT.

This joint is formed by the navicular bone and the flexor tendon, where the tendon articulates with the bone, being a circumscribed cavity, which is abundantly supplied with synovia, or joint oil, to lubricate and prevent friction between the internal polished surface of the tendon and the smooth cartilage covering the navicular bone.

The advanced stage of the disease is a total destruction of the joint, and which is so completely disorganized, that it can no longer act as a joint. There is not a drop of synovia to be found in it. The cartilage covering the navicular bone next the tendon is either entirely absorbed, or else in a complete state of ulceration; and the corresponding surface of the flexor tendon, which was before as smooth as the highest polish, has now become Description of rough, and the delicate and sensitive membrane joint. lining it, abraded; and in most cases of long duration there is a strong adhesion of the tendon to the

the diseased

Thick strong hoofs most pre

vicular lame

ness.

navicular bone. When this adhesion, or morbid insertion of the tendon into the bone, is present, there is generally, exclusively of the loss of cartilage, a diminution also of the navicular bone itself, leaving a hole in its centre formed by absorption.

In the earlier stage of the complaint, there is a deficiency of synovia, but not a total absence of it; the secreting or synovial membranes highly inflamed; an absorption of part of the cartilage of the inferior surface of the navicular bone, more particularly in the centre; and a roughness of the corresponding surface of the tendon. At this crisis there is only a slight adhesion of the tendon to the bone.

In very recent cases I have not found the tendon adhering to the bone, but I have invariably perceived a lesion or abrasion of a small portion of synovial membrane from the tendon, and generally that part of it which is opposed to the centre of the bone, exhibiting small streaks or shreds in the tendon; whilst the cartilage covering the corresponding part of the bone has appeared discoloured.

This disease more especially attacks that very disposed to na- foot which we are in the habit of calling a strong one, where the fibres of the horn are firm and tough, the toe thick and round, the wall or quarters strong, and high at the heels; the bars strong and deeply buried in the foot; the sole thick and concave. Such a foot is not so much disposed to approxima

tion of the heels as it is to the occult or partial con

traction.

the hoof, and

A slight stricture is observable round the middle Constriction of of the crust, or towards the upper part. When indentations. this is not present, there is invariably an indentation or slight falling in of one quarter, generally the inside quarter, though I have observed this on the outside.

With regard to ossification of the cartilages of the foot, and ossification of portions of the ligaments of the navicular bone, and other bony excrescences within the foot, I would remark, that, having dissected so many extreme cases of chronic foot lameness of some years' standing, in which I have found all the ravages of this disease limited to a space within the joint not exceeding half an inch square, and unaccompanied with the slightest disease of any other part of the internal foot, I am induced to consider them as mere effects arising out of the navicular disease; and more particularly, as there are far more groggy feet without the slightest ossification of the ligaments of the navicular bone than with them. In short, I think those who have recently described the navicular disease an ossification of the joint, have erred very much; for it is any thing but an excrescence or exostosis, a great loss or absorption of bone being, in fact, the malady: yet I must acknowledge that I have occasionally seen, in recent cases, a few small eminences on the inferior surface

On the descent

of the navicular joint.

of the centre of the bone, about the size of millet seeds; but, in the progress of the disease, not only would they have been absorbed by friction, but that portion of bone itself on which they appeared would also have been carried away by ulceration.

REMARKS.

It affords me no slight gratification, that my experience in the feet of horses, as far as it has yet gone, enables me to bear testimony to the truth of very many important points on the foot of the horse, as promulgated by that eminent head and father of our science, Professor Coleman: although I differ from him in practice; and, with respect to the physiology of some important parts of the foot, I must also somewhat differ from the same high authority.

Mr. Coleman says, that the navicular bone is very limited in its action; and necessarily so, first, by the shortness of its ligaments, which confine it to the coffin and small pastern bones; and, secondly, by being so closely bound by the flexor tendon, just previous to its insertion into the inferior concave part of the coffin bone.

I am of opinion that the navicular joint, being a double joint, adds much to the complicated mechanism of the foot; and as the end of all joints is motion, Nature certainly intended it to have considerable action, although its sphere of motion appears very limited.

With regard to its short ligaments, it must be remembered that it is never required to descend, except in connexion with the small pastern and coffin bones; and, therefore, even viewed as a process of the coffin bone, the shortness of the ligaments is in favour of its descent.

As to the binding appearance of the expanded part of the flexor tendon, this does not, in reality, impede its descent, because, at the instant the navicular bone descends under the weight received from the small pastern, the fibres of the flexor perforans muscle are relaxed, and consequently the muscle and tendon are elongated.

of motion in the

observable in

I wish it particularly to be understood, that I as- Great freedom cribe this great freedom of action in the navicular navicular joint bone only to very sound and good-actioned horses; clever hacknies and, to use a horseman's phraseology, the choicegifted hackney, which is said to put his heel down as freely as his toe. Riding men know-what the driving men are not aware of-that it is this sort only which is fit to ride.

Now, let us suppose a narrow-heeled horse (one whose feet are somewhat contracted, or suspicious as they are frequently called, but yet known always to have been free from lameness) to be loose in a large box, except during his two or three hours' daily work, which we will say shall average from six to ten miles an hour; let such a horse have, in addition to the indulgence of a well-strawed loose box,first, a groom who will periodically use the stopping