48. At five years off the corner teeth only show slight wear, and the posterior margins are round. Much of the original coating of the crusta petrosa is retained, but in colour it may not at this time be dark. At those places where it has been recently worn down, it is often of a yellow tint, which is but a little deeper than the enamel, which last, however, is nevertheless easily distinguished by its greater transparency and more pearly appearance. This peculiarity in the crusta petrosa not unseldom gives to the six year old mouth a darker aspect than is presented by the teeth of the younger animal; and the author, to convey to the reader some idea of this fact, has purposely rendered the incisors of the next representation of the mouth, as they frequently are seen. Such a circumstance, however, will not confuse the judgment. The corner nippers still look young to him who is acquainted with those signs which denote youth in the horse’s teeth, and the coloured engraving will convey a fair idea of the aspect they now put on. The corner nipper, in fact, after the fourth year, leads, in a great measure, if it does not entirely sway, the judgment. This tooth is sometimes called the shell tooth, on account of its infundibulum being, for the most part, better exhibited and longer retained than in the other incisors. The tables, however, of the other teeth should also receive some attention: those of the centre nippers may exhibit the infundibula shallow, or, in certain instances, when the crusta petrosa which lines these cavities is very thick, no infundibula may be distinguishable: even then, however, on close inspection, the form of the cavity will be discovered, marked out by a line of enamel, and the space that is usually vacant filled up with a substance, which in appearance differs little from the ivory. The tables of the lateral incisors will be fully formed, and the infundibulum is rarely obliterated, while its margin is always circumscribed and well defined, as the previous wood-cuts will indicate.
FIVE YEARS OFF.
The Corner Teeth only show slight wear,
and the posterior Margins are round.
SIX YEARS OFF.
The Corner Teeth look more firmly set,
and their edges begin to be uneven.
49. At six years of age, the corner teeth look more firmly set, and their edges begin to be uneven; they have become more square in the figure of the external surface; the edges of the teeth, when the mouth is closed, fairly meet; the round appearance of the posterior border is nearly lost, and the teeth are altogether of a most prominent character. The table of the corner teeth, nevertheless, is still confined to the part anterior to the infundibulum, which cavity is not yet fairly circumscribed or surrounded by a level margin. The infundibula may be lost in the central incisors, and those of the lateral teeth may begin to look shallow; but more generally these cavities are retained at six years old. The tables, likewise, have somewhat changed their positions, and the semi-circle which they formed at the fifth year, now is hardly so perfect, though still well marked. The above description will be the better understood by reference to the coloured engraving, which has been compared with the mouths of numerous animals, viz., Skeleton Sorella, and a brown horse, the property of Mr. T. Brown, &c., &c. The reader, however, will at once recognise the general truth of the drawing, the purpose of which the accompanying wood-cut will serve to explain. The alteration in the semi-circular arrangement will be better perceived by contrasting the present diagram with the one which preceded it, and though the change may not seem very great, nevertheless, sufficient is indicated to instruct the eye accustomed to observe it. The corner teeth have now acquired a degree of surface which will fairly represent a table, though it is still imperfect. The more darkly shaded portion of the separated table denotes the part which has yet received no attrition, but notwithstanding it is readily discerned that the nipper has come into active use.
50. At seven years off, the corner teeth, without showing age, exhibit further evidence of wear. The coloured engraving to which the reader must refer, exhibits those alterations which have now taken place. The original sketch was made from the mouth of a horse in the possession of the author’s father, and having been corroborated by the inspection of numerous others, it is confidently put forward as characteristic of the age. I cannot here forbear from acknowledging the personal kindness and professional attention bestowed upon me by Mr. Percival, who, on being made aware that I was engaged upon a work illustrative of the horse’s teeth, not only allowed me to inspect the mouths of the animals under his charge, but honoured me by accompanying me and assisted my endeavours to arrive at a just conclusion by his remarks. I have also to express my thanks to Mr. Braby for the liberty to inspect the large stud of heavy dray horses in the stables of Messrs. Barclay and Perkins, the eminent brewers. The advantages I derived from comparing so many mouths of the same age at the same time, and the facilities which were given of minutely examining each, enable me with more certainty to speak upon a subject which otherwise it would have been prudent to mention only in the most qualified terms. However, after such ample investigation, I can, with confidence, refer to the plate depicting the mouth at seven years off. Looking at it, the reader will see the teeth have become more white, in consequence of the crusta petrosa having, by the natural wear, been to a greater extent removed. The tushes are exhibited as fully up, in which condition they are generally seen. Where the corner teeth meet, they close in such a manner as denotes considerable use. The way in which the gums encircle the necks of the shell teeth has also changed. By referring back to the engraving of the five-year off mouth, the difference will be more readily understood, the round arrangement of the gums at the earlier age being very significant. The tables of the teeth, however, at this period ought never to be overlooked; they afford, perhaps, the best indications on which the judgment can be based. The infundibula may or may not be gone in the lateral teeth; but those of the corner teeth have at this age become defined. Where the corner teeth meet, in consequence of those of the lower jaw being, in many horses, a little the most forward, the upper shell teeth may present posteriorly a small projection, which is seldom seen prior to the seventh year. When this is present, it is so obvious as not to escape observation, therefore, it has not been depicted in the coloured engraving, which has purposely been made to represent the less marked indication that is more difficult to judge by. The reader will see the projection alluded to slightly indicated in the previous coloured engraving, portraying the mouth at six years off. Where the two shell teeth meet, he will observe that the most backward portion of the upper, not being opposed by the lower tooth, and consequently suffering no wear, bulges slightly downwards. It is this particular part, which often at the seventh year, by the wearing down of the upper tooth, becomes so apparent as to be significant of the age. It is, however, not constantly present, and the tables consequently become of the greater importance, as they are always to be found. Those of the lateral incisors begin to depart from their oval figure, and those of the central nippers are growing decidedly angular: the tushes may have the edges slightly rounded, and the semi-circle which the tables of the incisors formed when the animal was five years old, may exhibit some inclination to change in favour of the lineal arrangement that is in many horses so prominently marked in old age. This semi-circular arrangement of the incisors is most conspicuous when the colt is rising five; and from that period gradually alters, till in very old subjects the tables will occasionally be ranged almost in a straight line. The alteration which takes place in this respect is, however, by no means uniform, and though, consequently, no rule can be absolutely laid down concerning it, yet, from the known inclination of the teeth to assume a certain figure, an inference can be drawn which, connected with other signs, enables a pretty close opinion to be formed. At the seventh year, however, the corner teeth, their external figure, and the form of their tables, taken in conjunction with the wear exhibited by the central and lateral incisors, and considered with the narrowed but not yet sharp edge of the lower jaw, enable the judge to arrive, with tolerable certainty, at a conclusion. The following representation of the tables, taken in conjunction with the coloured engraving of the seven-year old mouth, will convey an idea of its appearance at that age. The reader will remark the infundibulum of the corner tooth has become circumscribed, being now encircled by a flattened surface, which posteriorly is of some width.
