MASTICATION. 253 



molars in the upper and lower jaws. In front of the molar teeth there 

 are sometimes rudimentary teeth, which are called wolf-teeth. In the 

 horse the molar teeth have their grooves produced by the cement ar- 

 ranged longitudinally on the crown. In the stallion there are twelve 

 incisors, — six in each jaw, of which the upper are the longest, while the 

 central are the largest and the corner teeth the smallest,— four canine 

 teeth, and twenty-four molars ; in all forty. In the mare there are thirty- 

 six teeth, the canine teeth being wanting. The free surface of the incisor 

 teeth, with the exception of the table, is covered with enamel, while the 

 fang is covered with cement. As the incisor tooth comes through the 

 jaw the cement which originally covered the entire body of the tooth 

 remains on the table of the tooth in a depression which is called the 

 infundibulum. As the enamel of the table of the tooth wears away 

 around this central infundibulum the dentine of the body of the tooth 

 within is gradually exposed. We, therefore, have three different substances 

 composing the table of the incisor teeth of the horse (see Figs. 95 and 

 96), — the outer ring of enamel; within that, concentrically, the exposed 

 dentine ; and within that again the more or 

 less triangular ring of enamel which com- [\ ----s 



posed originally the wall of the infundibulum, 

 and which was continuous with the enamel 

 covering the crown of the tooth. Within , , , 



this, again, is a more or less circular or tri- 

 angular portion of cement by which the 

 infundibulum was originally filled. Occa- 

 sionally in front of the infundibulum a still 

 denser substance than the dentine will be Fig. ioo.— incisok Tooth of 

 met with, which is called osteodentine, and , \ \. ' , ! ' 



' e, enamel; a, dentine.; c«, pulp-cavity. 



which is due to the exposure of the ossified 



covering of the pulp-sac. This is also called the dental star. Two sets 

 of teeth are found in the horse, of which the first, or milk-teeth, are 

 wider and have distinct necks, are convex and are grooved posteriorly. 

 The incisors at first are almost perpendicular, but become more and more 

 horizontal as the teeth wear down ; the lower permanent incisors have 

 one groove, the upper two. 



In ruminants thirtj'-two teeth are met with, the incisors being found 

 only in the lower jaw. Eight incisors and twenty-four molars are met 

 with. The incisor teeth in the ruminant are always somewhat loose, their 

 table is always inclined, and the anterior border sharp (Fig. 100). The 

 molars are compound teeth which wear down and continue to grow even 

 to an advanced age of the animal. The inferior molars have their tables 

 inclining outwardly, the upper incline inwardly, while, as in the solipedes, 

 the molars of both sides cannot be in apposition at the same time, since 



