216 MANUAL OF MODERN FARRIERY. 



easiest come at are the incisors. The supplementary 

 molars appear in the following order : the first, at about ten 

 or eleven months ; the second, about twenty months ; and 

 the third, from four to six years of age. 



The incisor teeth are continually undergoing some change, 

 in consequence of the friction produced by the action of 

 their rubbing against each other. The anterior edge being 

 considerably more elevated and sharper than the posterior, 

 the wear first commences there, and in a short time it 

 is level with the posterior, then both wear together ; the 

 longitudinal cavity becomes narroAver, and afterwards tri- 

 angular, and, finally, at a certain period disappears, and 

 is replaced by the small end of the funnel next the root ; it 

 is this regular wear which is termed " losing the mark," (see 

 fig. 4.) The obliteration of the mark has frequently taken 

 place by the time the corner teeth are beginning to appear. 

 It must be distinctly understood, that in speaking of the 

 marks in the tooth we constantly refer to the incisors of the 

 under jaw, except when otherwise expressed ; and the ages 

 of all horses are reckoned from May. 



When an incisor tooth has commenced wearing, and its 

 two edges are parallel, the table exhibits two bands of 

 enamel, the one exterior, that surrounds the tooth, which is 

 termed the casing enamel ; the other internal, only sur- 

 rounding the cavity, and this is called the central enamel, 

 (see plate iv. figs. 3 and 5) The incisor teeth of the lower 

 jaw always wear more quickly than those of the upper, and 

 uniformly more regular. The reason of this has never been 

 satisfactorily accounted for, but it is certainly very remai'k- 

 able. From this fact it is obvious that it is more difficult 

 to judge of the period of obliteration of the mark in the 

 upper jaw. In the lower jaw the marks of the nippers, or 

 central incisors, are always obliterated at ten months ; in 



