The foal may be said to come into the world toothless; at least, he shows none of those teeth which, in after years, become the criteria of age; to wit, the incisive teeth and the tusks. To make use of a phrase well understood among medical men, the foal at birth is only in the act of cutting twelve of his 'grinders; three in each jaw. Although he shows no front teeth, he nevertheless possesses them ; they being buried, ready-formed, within the jaws, and now about to pierce the gums, which are, in consequence thereof, more prominent in those places than elsewhere.
About the expiration of the first week after birth, or in the course of the second, the front incisive teeth cut the gums; and these are succeeded, in the course of the fourth or fifth week, by the middle teeth, which spring up on their sides: the teeth in the upper jaw making their appearance commonly before those in the lower,—a remark that applies to the cutting of the teeth in general. So that if you. on distracting a colt's lips, find that he has only four nippers, two in each jaw, you will know that he is a week old, as is represented by Fig. 1, Plate DXXXII.; on the other hand, if, instead of four, he possesses eight teeth, you may know he has been dropped at least a month. Tide Fig. 2.
By the time the foal begins to look about for food of a more substantial kind than that afforded by its darn, these fuur teeth have made sufficient progress to enable the animal to nip its pasture and browse, or gather up dry provender ready cut for it: also, about this period—about the sixth or se venth month—the corner teeth make their exit; and by growing and forming a line with the others, complete the colt's set of incisors. Vide Fig. S.
These (colt's) teeth continue to serve the animal until after he has completed his second year; and they remain all this time, to a casual or superficial observation, without any change or alteration: if, however, we will only take the trouble to compare the teeth of an yearling with that of a two-year-old colt, we shall discover ample marks of distinction to enable us to pronounce, without fear of being in error, whether the colt be one or two years of age. The Figs. 3 and 4 will serve to demonstrate this difference. It will be seen in the former that the teeth are represented as possessing large, open, deep pits upon their surfaces, which denote their imperfect formation: whereas, in the latter figure, the teeth (particularly the two in the middle) pos.
sess nothing but contracted faint black marks, show ing the situations of the original pits, now filled up by a process of growth and consummation. When, therefore, we come to make a calculation grounded on the progress of growth, as indicated by these changes, and take into our account the general law of dating every horse's age from the first of May, (without any reference to the clay or month in which he was foaled) we shall experience no difficulty in numbering his months as well as his years.
Between the second and third years, the "shed ding process," as it is phrased, commences; i. c. the colt's teeth, in consequence of absorption of their fangs or roots, gradually lose their hold, and at length fall out, to make room for the permanent or horse's teeth, which are springing up underneath them. The front teeth are the first to make this change; and they are found regularly to do so as the animal approaches his third year: so that as soon as they have made their appearance, we know that the colt is either close approaching or •past his third year, dependent upon the month of May being either past or to conic. ride Fig. 5.
Between the third and fourth years, the middle teeth undergo the same changes; and between the fourth and fifth years, the corner teeth: so that the animal is readily pronounced to be in his fourth or fifth year, according as he has six or eight horse's teeth. ride Figs. 6 and 7. In addition to which, as a further confirmation of his age (were any re quired), the tusks commonly make their appearance about the fifth year; as is shown by Fig. 7.
The fifth year being the period at which the ani mal is provided with his full set of permanent teeth, we are henceforth compelled, in order to judge of his age in after years, to seek for other signs: and observation and experience have taught us, that such are to be met with in the alterations which the teeth themselves undergo ; and further, that these marks of age are hardly less unequivocal than those afforded by the shedding process. The alter ations alluded to are more particularly demonstra ble upon the wearing surfaces or faces of the inci sive teeth; and they take place with such regularity, year after year, that we are enabled, by comparison of one with another, to come to pretty correct con clusions. A fresh-cut tooth, for example, exhibits upon its face a•wide open pit, the elliptical border around which is prominent and rather sharp, ante riorly; but low and defective, posteriorly. During the first year afterwards, the border all around the pit attains the same level, and subsequently becomes worn down so as to exhibit two prominent white elliptical rings surrounding the pit, which itself y cry gradually contracts and fills up, and acquires internally a black aspect; which has given rise to the appellation of bean or mark. In the course of the second year, the rims become worn down smooth and level with the surface, and the pit, though still well marked, grows evidently narrower and shallow er. In the third year from its eruption, the tooth exhibits but faint vestiges of the white rims; the pit becomes filled up, and the black mark in its middle converted into a mere stripe, or it may be altogether effaced.