56 



AMFjnc.W Mr SKIM (,ril)E LKM'LETS 



D 



niiiid that the horse's teeth are not full\' fune- 

 lional until tlie folded e(lji;es of enamel (jn the 

 ^rindin^ surface are woiii through to the 

 dentine. 



Fi^ui-e 33/y shows the deciduous upper 

 molar [<\. in. ) of a colt about three months 

 hefoi'e hiilh. The enamel of the culs-de-sac is 

 continuous with that of the exterior, the folded 

 v^V^v:^ on the «iiin(lin<i- surface heinj^ unworn. 

 It is as yet entirely without cement so that we 

 have an unobstructed view of the enamel. 

 When the colt is six months old, however, 

 the culs-de-sac will be practicalh^ filled with 

 cement and also the deep folds of the exterior 

 (Fig. 33.4), the deposit of cement beginning 

 about a month before birth. 



We have seen that the permanent incisors 

 are much more highh' specialized than are 

 the deciduous ones (Page 48). This is quite 

 as noticeable in the grinding teeth. Observe 

 the wonderful development of enamel edges in 

 figure 33C'. This is a premolar of a horse eight 

 or nine years old. A careful measurement of 

 the exposed enamel in this tooth reveals the 

 interesting fact that if these edges were straigh- 

 tened out in a continuous line, it would ho 

 fourteen inches in length. In a tooth of this 

 size on the simple ''cylinder" plan, it is 

 obvious v.-e would have only a])out four inches 

 of enamel, hence we can wilUngly concede 

 nature's wisdom in this comparatively "mod- 

 ern improvement." 



This enamel pattern however, presents a 

 more simple aspect as the tooth wears down 

 toward the base of the crown, so that in old 

 age when the grinding surface is near the root, 

 there is less enamel, and the self-sharpening 

 surface is much less perfect. The antero- 



I I &na-yyiel 



W^ dentiPte 



^ cement 



■ yvatu^val cavity 



Fi<i. :U. Upper grinder (/). m. ■*-) of horse 10 or 

 11 years old cut in o sections; showing pattern of 

 enamel at various ages 



vity 



r, /(. 



E. h. 



Branches of the pulp 

 Pulp cavity 



