116 THE STRUCTURE OF THE HOESE. 



horse-like animals, show them to be teeth which, for 

 some reason to us at present unknown, have become 

 superfluous — have been very gradually and slowly (as 

 in the case of all operations of the kind) dispensed 

 with, and are in the stage to which the horse has now 

 arrived in its evolution, upon the point of disappear- 

 ance. The presence of these so-called " wolves' 

 teeth " alone is sufficient, if we had no other proof, 

 to show that the horse is not an isolated creation, 

 but one link in a great chain of organic beings. The 

 fact that these teeth are almost always met with in 

 the upper jaw only, should be noted in connection 

 with what has been previously mentioned respecting 

 the dentition of the tapir. The first upper premolar 

 is retained in that animal, while the corresponding 

 lower tooth has entirely disappeared. 



It would be very interesting, if a sufficiently large 

 number of specimens could be examined, to obtain 

 some statistical imformation as to the relative fre- 

 quency of the occurrence of these teeth in the differ- 

 ent species of wild and different breeds of domestic 

 horses. They are usually so loosely attached in the 

 skull that they become lost in specimens prepared 

 for museums ; but indications can generally be seen 

 on the bone, if they have been present. 



General Characters and Structure of Teeth. — Before 

 describing the teeth of the horse a little more in de- 



