EXPLANATION

OF

PLATE IV.

OF THE MUSCLES OF THE FACE OF BRUTES.

THE first figure of this plate is a sketch by Mr. Northcote, and exhibits the natural character of the horse's head, in illustration of the anatomy demonstrated in the second figure.

Fig. 2. represents the muscles of the horse's head.

A. A. The orbicular muscle of the eyelids.

B. An accessory muscle to raise the eyelid.

c. A very peculiar muscle, since it pulls down the eyelid.

D. A muscle connected also with the eye, and arising from the

cartilages of the ear.

E. A muscle answering to the zygomatic muscle in man.

These muscles, surrounding the eyelids of the horse, account for the superior expression of the eye. The muscle D seems to be calculated to operate upon the outer angle of the eyelids, and to enable the animal to direct the eye backwards: in this it is probably assisted by the muscle E.

F. This forms a class of muscles which descend on the side of the face, and are inserted into the nostril.

G. G. Muscular fibres, also operating in the distention of the tube of the nostril.

H. A strong muscle, which acts upon the cartilage, and distends the nostril with great power.

There is something in the distribution of these muscles which illustrates the character of the class, and accounts for the peculiarity of expression. We cannot fail to observe the difference in the general direction and classing of the muscles of the face in the horse and in the dog. In the carnivorous animal they all tend to lift the lips from the canine teeth, so that they cannot act without showing the teeth with the snarling expression; here, on the contrary, muscles having the same place and origin pass to the cartilages of the nose, and inflate it the instant that they are excited. It is therefore these muscles, more than any other circumstance, that produce the very different character and expression of the two classes of animals, the Carnivorous and Graminivorous.

1. A strong muscle, which lies under those of the nostril F. Its tendon passes forward over the nose, and unites with its fellow of the other side. These together form a broad tendon, which is inserted into the upper lip. There is a similar muscle moving the lower lip, which cannot be seen in this view. L. M. The circular fibres of the lips, which in the horse are particularly strong and fleshy.

N. A web of muscle, which is extended from the cutaneous muscle of the neck.

The muscles 1. K. L. M. have all great power, and give extensive motion to the lips. K. is the tendon of the muscles of the upper lip, which I have called DEPASCENTES: it takes this course over the nose in a manner quite peculiar to this class of animals, to raise and project the lip as in gathering its food. Any one who feeds his horse from his hand may feel the singular sensitiveness and mobility of his lips.

Looking to these muscles, and contrasting them with the animated sketch above it, we cannot fail to see how much the form of the head has to do with the teeth-small forward, and large and deep set in the back part of the jaw; and how much the peculiarity of expression of the animal is owing to the breathing through the nostril, and not through the mouth; and to the brilliant eye placed on the utmost projection of the head, and which, by the slightest turn of the pliant neck, is directed backward; and, finally, how the