However, while the milk tooth is retained in the mouth the neck is not particularly well shown, because the gum encircling the crown in a great measure conceals that part. But the form of the outer surface of the crown can hardly be mistaken. In the foal's tooth it more or less approaches to a semi-circle, from which the permanent teeth greatly differ, as will be seen by comparing the representations of the two as given in the plates. The outer surface likewise is characterized by peculiar indentations: a number of small channels run along it, taking a course from the neck towards the margin of the table, and giving an irregular fluted appearance to the enamel. There will be seen, on the crown of _Figure_ 2, lines intended to convey an idea of the situation and direction of these little grooves. The table is always oblong, but the infundibula are generally absent after the second year, and when they are present, the cavities are narrow, and obviously of little depth. These numerous signs enable the milk tooth to be recognized with facility, at a single glance, for it is seldom that one of the various indications is absent; and after all have been impressed by observation, the milk tooth can hardly be mistaken. 26. _The permanent incisors are indicated by their greater size_, a circumstance which the foregoing wood-cut does not exaggerate. The gum is much further retracted, and this gives to these organs an irregular oblong figure, which is very different from the semi-circular shape of the milk teeth. The incisors, however, are not of equal length in all horses, and in some the gum may be so prominent as to give the permanent somewhat the appearance of a temporary incisor; other indications, however, even then, enable the different nature of each to be with certainty distinguished. The enamel is only partially exposed in the horse tooth; the shaded portion of _Figure_ 1, in the preceding wood-cut, denotes the extent to which it is generally covered during the period of dentition; and when the teeth first appear, the enamel is wholly concealed by a covering of crusta petrosa. That covering is never entirely removed--a small portion of it, even in the oldest mouths, is seen near to the gums. It looks like an accumulation of tartar, and is most conspicuous in the tooth that has been newly cut. The presence or absence of this substance, therefore, should be noted, and moreover, the enamel surface should be further inspected. The numerous channels that give so peculiar a fluted appearance to the milk tooth, are not to be seen upon that of a permanent description; but in the stead are to be detected only one or two broad grooves, which extend the entire length of the crown. _Figure_ 1, at page 48, indicates the shape and direction of the grooves upon the surface of the permanent tooth, though probably a better idea of them is to be derived from an inspection of the coloured engravings, in which they are more prominently exhibited. By