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 narrower, 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 comer 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 remark¬ 
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 
