24. _To know the temporary from the permanent teeth_, or to be able to distinguish one from the other, is very essential; but such knowledge is not so common as may be generally imagined. Dealers have blundered, and many a gentleman having purchased a yearling for a horse, has afterwards been surprised to discover that the animal was losing some of its front teeth. These kind of mistakes are mostly confined to the smaller breeds--with ponies the incident is common enough, but even with horses it has occurred. I may therefore be excused if I enter rather minutely into those points of difference which distinguish the one from the other. The reader must be content to study well this portion of the treatise, for the age is best marked by the number of milk teeth retained in the jaw, and easiest told during those years when these teeth are in the course of being shed. 25. _To recognize a milk incisor tooth_ the reader must bear in mind that it is of a temporary nature, and intended only to exist during the few first years of the animal's life, or during its colthood; for when all the permanent teeth are fairly up, the creature becomes a horse. The recollection of their temporary character will cause them to be the more easily distinguished: they look less solid and less firm; they are smaller, more white, and if ideas of beauty and sentiment befit such a subject, have a prettier and more innocent appearance. This is perfectly true as a general rule, but nevertheless must not be absolutely applied; for I have seen rare instances in which the milk teeth were, from constitutional or other causes, so discoloured, as altogether to lose their infantine and prepossessing character--the permanent incisors appearing cleanly by the contrast. On account of so singular a circumstance occasionally happening, if for no stronger reason, it is imperative therefore, even at the risk of being tedious, to enter minutely into this part of the subject. In colour these teeth are white, because the coating of crusta petrosa which originally invests them is particularly thin, and soon, for the most part, disappears, exposing the enamel; their crowns are shorter, and the neck is well developed, because their fangs are narrow and of less length. In the annexed wood-cut, for the purpose of making the dissimilarity the more conspicuous, a temporary and a permanent incisor are contrasted. _Figure_ 1 is the horse, _Figure_ 2 the milk tooth. The fang of the milk tooth is properly represented of considerable less diameter than the crown; and just where it arises will be observed a little shading, which indicates a sinking in, or nipping up, at that particular spot: the place so narrowed is the neck, which in the temporary teeth of the colt is not badly developed. [Illustration: _Fig._ 1.] [Illustration: _Fig._ 2.]