Page:The Horse.djvu/154

146 are smaller, and narrower, and more regular, than the upper ones. They are placed horizontally in either jaw; but in the lower the higher side is within, and shelving gradually outward; in the upper jaw the higher side is without, and shelving inward, and thus the grinding motion is most advantageously performed. There is also an evident difference in the appearance and structure of each of the grinders, so that a careful observer could tell to which jaw every one belonged, and what situation it occupied.

At the completion of the first year, a fourth grinder usually comes up, and the yearling has then, or soon afterwards, six nippers, and four grinders above and below in each jaw, which, with the alteration in the appearance of the nippers that we have just described, will enable us to calculate nearly the age of the foal, subject to some variations arising from the period of weaning, and the nature of the food.

At the age of one year and a-half, the mark in the central nippers will be much shorter and fainter; that in the two other pairs will have undergone an evident change, and all the nippers will be flat.

At two years this will be more manifest. The accompanying cut deserves attention, as giving an accurate representation of the nippers in the lower jaw of a two-years-old colt.

About this period a fifth grinder will appear, and now, likewise, will commence another process. The first teeth are adapted to the size and wants of the young animal. They are sufficiently large to occupy and fill the colt's jaws; but when these bones have expanded with the increasing growth of the animal, the teeth are separated too far from each other to be useful, and another and larger set is required. Evident provision is made for them, even before the colt foaled. In cavities in the jaw, beneath the first and temporary teeth, are to be seen the rudiments of a second and permanent set. These gradually increase, some with greater rapidity than others, and, pressing upon the roots or fangs of the first teeth, do not, as would be imagined, force out the former ones, but the portion pressed upon gradually disappears. It is absorbed—taken up and carried away, by numerous minute vessels, whose office it is to get rid of the worn-out or useless part of the system. This absorption continues to proceed as the second teeth grow and press upwards, until the whole of the fang is gone, and the crown of the tooth, or that part of it which was above the gum, having no longer firm hold, drops out, and the second teeth appear, larger and stronger and permanent. In a few instances, however, the second teeth do not rise immediately under the temporary or milk teeth, but somewhat by their side; and then, instead of this gradual process of absorption and disappearance from the point of the root upwards, the root being compressed sideways, diminishes throughout its whole bulk. The crown of the tooth diminishes with the root, and the whole is pushed out of its place, to the fore part of the first grinder, and remains for a considerable time, under the name of a wolf's tooth, causing swelling and soreness of the gums, and frequently wounding the cheeks. They would be gradually quite absorbed, but the process might be slow and the annoyance would be great, and, therefore, they are extracted.

The change of the teeth commences in those which earliest appeared, and, therefore, the front or first grinder gives way at the age of two years, and is succeeded by a larger and permanent tooth.

During the period between the falling out of the central milk nippers, and the coming up of the permanent ones, the colt, having a broken mouth, may find some difficulty in grazing. If he should fall away considerably in condition, he should be fed with mashes and corn, or cut meat.

The next cut will represent a three-years-old mouth. The central teeth are larger than the others, with two grooves in the outer convex surface, and the mark is long, narrow, deep and black. Not having yet attained their full growth, they are rather lower than the others. The mark in the two next nippers is nearly worn out, and it is wearing away in the corner nippers. Is it possible to give this mouth to an early two-years-old? The ages of all horses used to be reckoned from May, but some are foaled even so early as January, and being actually four months over the two years,