I shall here of course omit to describe parts, such as the eyes, head and tail, for instance, which are known to everyone. The figures and letters employed in the following list, have reference to those on [Fig. 147], except when [Fig. 148] is mentioned.
The hoof (10) is the horny box which encloses the lower part of the leg. The front part of the hoof, near the ground surface, is called the toe; the side portions, the quarters; and the rear parts, the heels. The outer portion of the hoof is termed the wall, which is divided into a hard, fibrous outer covering, called the crust, and a soft inner layer of non-fibrous horn. The designations “wall” and “crust” are often used indiscriminately.
The frog is the triangular horny cushion which is in the centre of the ground surface of the hoof, and which, by its elasticity and strength, acts as a buffer in saving the structures inside the hoof from the injurious effects of concussion.
The cleft of the frog is the division in the middle line of the frog. In healthy feet, it consists of only a slight depression. In a disease, called “thrush,” of the sensitive part which secretes the frog, the cleft forms a deep, damp and foul-smelling fissure, and the frog becomes more or less shrivelled up. The frog similar to the skin of the palms of our hands, requires frequent pressure to make it thick and strong. The horn of the hoof is merely a modification of the cuticle (scarf skin).
The bars of the hoof are the portions of the wall of the hoof which are turned inwards at the heels, and run more or less parallel to the sides of the frog. The sole is that portion of the ground surface of the foot which is included between the wall, bars and frog.
The pastern (9) is the short column of bones (two in number) which lies between the fetlock and hoof.
The fetlock (8) is the prominent joint which is just above the hoof.
The cannon bone (7) is the bone that extends from the fetlock to the knee (6), which, in the horse, corresponds to our wrist.
The back tendons or back sinews (M) form the more or less round tendinous cord which is at the back of the leg, from the knee (or hock) to the fetlock. These tendons, which are two in number, usually appear in the form of one cord; but in horses which have a very fine skin and “clean legs,” we may see that one of them is placed behind the other. The term “clean legs” signifies that the limbs are not only sound, but are also free from any fulness, which would more or less obscure the contour of the bones, tendons and ligaments. Muscles are the lean of meat, and their ends are connected to bones by means of tendons, which consist of hard, fibrous and inelastic material. The ligaments of the limbs are composed of the same material (white connective tissue) as tendons, and serve to connect bones together, without the intervention of muscle. The horse has practically no muscles below his knees and hocks.