Fig. [5].
Horse’s Leg
I must, however, resist the temptation to wander into this attractive field. It will suffice to take an illustration by a comparison of the bones of the human lower limb with those of the hind limb of the Horse. This may be easily done by the aid of these drawings (figs. 4> and 5) in which the two limbs are placed side by side, and the corresponding bones are marked with the same letters. Notwithstanding the many points of difference the same plan will be recognised in each. There is in each the thigh(C), the leg(E), and the foot, with the tarsal and metatarsal(G) bones, and the phalanges(H, I, K). But in the Horse two of the digits (the marginal ones, that is, the great toe and the little toe) are wanting, two are rudimentary, and the remaining one, which corresponds with the middle toe of man, in length, size, and strength, more than makes amends for the deficiency of the others. The lowermost bone, or terminal phalanx, of this huge toe, called the coffin-bone(K), is encased in the hoof, which corresponds with the human nail, and is the only part of the foot that rests upon the ground.
In Man the whole weight of the body has to be borne upon two feet; often it is balanced upon one. The foot is, consequently, spread out; and all the bones, from the heel to the tips of the toes, are made to form the basis of support upon the ground. The Horse, on the contrary, having no hands, but four feet, does not require so great breadth in each foot; and the opportunity is taken to narrow the foot, and to lengthen it so as to give fleetness. The end is attained by suppressing some of the toes, by elongating one far beyond the others, and enduing it with such strength as to enable it to carry the requisite weight upon the tip of the last phalanx. The heel(F) is raised high above the ground and becomes the “hock.” To speak of a horse kicking with his heels is, therefore, about as correct as to say, that he breaks his knees. His knee, as you perceive by the position of the “knee-cap”(D), is high up in the hind limb, near his body, quite out of harm’s way in a fall. The fact is, that he kicks with his toes; and, when he falls, he cuts the skin over the part in his fore limbs, which corresponds with the back of our wrists.
In the upper segment, or thigh, the difference between the two limbs is seen to be, to a certain extent, the reverse of what it is below. That is to say, whereas, in the Horse, the toe is elongated and thickened, so as greatly to exceed the corresponding part of the human limb; in Man the thigh-bone is elongated, so as to be double the length of that of the horse; the thigh-bone in man is also placed more vertically, nearly in the plane of gravity of the trunk. The horse’s thigh-bone slants forwards and outwards, which gives the muscles great power by causing them to run more at right angles between their points of attachment; and this arrangement increases the strength of the animal in drawing weights, and facilitates springing. A man cannot spring without first bending the limbs a little; whereas a horse, or a goat, can spring, at once, from the position in which it is standing.
To revert to the anatomy of the Human Foot.
The Arch of the Foot.
The seven tarsal and the five metatarsal bones—that is, the twelve bones of the instep—are arranged and jointed together so as to form an arch from the point of the heel to the balls of the toes. This is called the “plantar arch,” from the Latin word planta, the sole of the foot. The astragalus forms the summit, or key-bone, of the arch. It receives the weight from the leg, and transmits it, through the hinder pillar of the arch, to the heel, and, through the front pillar of the arch, to the balls of the toes.
Fig. [6].