126 THE ARTISTIC ANATOMY OF ANIMALS 



The teeth of the horse are forty in number ; they are 

 thus distributed : 



= 40. 



As they become worn, these teeth continue to grow, and as, 

 on the one hand, this phenomenon takes place throughout 

 the whole life of the animal, and, on the other hand, the 

 process of wear brings out and makes visible at the surface 

 of friction parts formerly deeper and deeper, and of which 

 the configuration varies at different levels, there result 

 special features which permit the determination of the age of 

 the animal by an examination of its jaws. The incisors are 

 called, commencing with those situated nearest the middle 

 line, central incisors or nippers, intermediate and corner in- 

 cisors. The canines, also designated as the fangs, exist only 

 in the male. It is exceptionalto find them in the mare, and 

 when they exist in this latter they are less developed than 

 those of the horse. The molars have cuboid crowns ; the 

 surface of friction is almost square in the case of the upper 

 molars, and is inclined so as to look inwards ; in the case of 

 the inferior ones, it is a little narrowed, and is inclined so 

 as to look outwards. In the upper jaw the external surface 

 of the crown is hollowed by two longitudinal furrows ; 

 in the lower jaw the same surface has only one furrow, 

 which at times is but slightly marked. 



In the hare the teeth are twenty-eight in number : 



6m. oc. 2i. I 21. 00. 6m. 



. = 28. 



5m. oc. li. I li. oc. 5m. 



The four incisors of the upper jaw are divided into two 

 groups ; one of these is formed by the two principal teeth, 

 the other by two very small incisors which are placed behind 

 the preceding. 



Having studied the jaws and examined the arrangement 

 of the teeth, we should say a few words on the move- 

 ments which the lower jaw is able to execute. In 

 man, these movements are varied in character : the jaw 

 is lowered and raised ; it can also be projected forwards 



