54 AMh'h'IC.W MISKCM ClIDK LEAlLI-yiS 



known aiii()n«i dentists as bicuspids, the first one in the lower jaw would 

 1)0 expressed p. ///. ;f . The second would he />. ///. 4 , assuming that p. m. r 

 and />. fti. ■> are the missing teeth. The teeth of sj)eciniens on exhiljition, 

 Nos. 10 and .')(). aic lalx'led in the manner desciil)e(l. 



THE WOLF TOOTH OF THE HORSE 



IX the horse we may say tliat p. m. \ ( Fi^. .MB) is now in the last stage 

 of elimination. Just in front of the ujiper premolars there is fre- 

 (luently found a very small abortive tooth conunonly known as the 

 '' wolf tooth." It does also occur in the lower jaw but is very rare. It is 

 absolutely non-functional, and is in fact detrimental, as it sometimes 

 gives rise to more or less irritation. So that in the horse the first func- 

 tional premolar is p. m. 1. The wolf tooth, though interesting, is rather 

 hard to study owing to its irregularity. When speaking of the permanent 

 teeth it is generally designated as p. m. ~, which would be correct if it 

 really ])elonged to the permanent set; this, however, I am inclined to 

 doubt, although it is frequently found long after the shedding period is 

 over. Nevertheless, it seems highly pro])able that it is a deciduous tooth 

 which having no successor, is not shed. In this case it would seem that 

 the permanent tooth had ])een eliminated eai'lier in the course of evolu- 

 tion than the deciduous one. But until we have more conclusive evidence 

 on this ])()int ];)robal)ly it will be as well to include the wolf tooth among 

 the teeth with which we find it. In figure 32.4 there is shown the un- 

 usual occurrence of the wolf tooth in the lower jaw. In looking over the 

 fossil ancestors it seems this tooth began to show signs of elimination in 

 the late Oligocene Period, which is estimated to be about two million 

 years ago. At this rate we may reasonably hope for some few social re- 

 formsbefore the horse is entireh' rid of this rather unde>irable appendix. 



PREMOLARS AND MOLARS OF THE HORSE 



WHl-^X we compare the molar tooth with its most intricate struc- 

 tur(\ with the incisor, the latter seems perfect simplicity. 

 Without here discussing the evolutionary history of the tooth, 

 it is extremely interesting to consider these special adaptations, which are 

 merely gradual modifications of a simple form brought about without any 

 radical or sudden changes, but slowly (kn'eloixMl in an orderly and shall 

 we say, orthodox manner. 



The molar of the horse as we find it to-day is a wonderful structure, 

 pr(^senting on its giinding suiface a most complicated system of sharp 



