51. _At eight years off, the gum of the lower corner tooth has become square, and the lower tush blunt._ The original drawing was made from the teeth of that noted horse, Oakley; and in order to render it as perfect as possible, the mouths of mares (Meal, Edgworth, Bess, &c.) have been compared. The departure from the circular form of the gum, as depicted in the coloured engraving, is even more marked than it was at the seventh year. Added to this change of figure, the gums appear more hard and less delicate; the mouth looks more firm, and seems to have attained the perfection of its strength. The margin of the lower jaw is now comparatively sharp, and the cheeks are flat. The crusta petrosa on the upper teeth is in a great degree removed; the enamel not yet, however, having a marked yellow tinge. On the lower corner incisors the crusta petrosa may still continue, but it no longer has a dull brown aspect: it is never prominent at this age, but rather speckled over the outer surface, than regularly enveloping any portion of it. It has a somewhat rough and worm-eaten aspect, and in colour is nearer to a dirty yellow than a dull brown. If the posterior angle of the upper corner incisor is pendant, or exhibits that species of notch, which was alluded to in the previous paragraph, it is at the eighth year well shown, and the table has undergone considerable alteration. There is now on the shell tooth, a full table, the infundibulum of which, if not obliterated, is always of lessened size, well marked out, and on all sides surrounded by a broad and a flattened surface. The other teeth have also changed their figures. The tables of the centre nippers have taken on a decided angular shape, and those of the lateral display no dubious tendency to assume that form. The infundibula may be obliterated, but more generally those in the lateral and corner teeth are retained, or if now absent, the circle of enamel will, on inspection, show that the cavity is only filled up by crusta petrosa, not absolutely worn out. The following wood-cuts exhibit the changes which the tables undergo; and as the eighth year is an important one, inasmuch as the horse which has attained it is called "aged," a double set is here introduced, to show the difference of figure which these parts may present. In those tables, it will be seen the infundibulum has gone from a central nipper only; but even in that instance, a white mark indicates that the cavity is merely filled up by crusta petrosa, the enamelled lining not being yet worn out. The alteration in the form and magnitude of the infundibula cannot, if the accompanying wood-cut be compared with those which have preceded it, fail to strike the reader; indeed these changes, aided by the worn appearance of tables of the shell teeth, are now the principal guides when judging of the age by the mouth. [Illustration]