THE HEAD AM) NECK 



107 



Ungulate mammals, without exception, had on each side, 

 above and below, three incisors, one canine, four pre- 

 molars, and three molars — that is, eleven on each side 

 above, and eleven below, or forty-four altogether. The 

 modern horse has nearly, if not quite, this full number. 

 The front teeth, or incisors, are the same — six above 

 and six below, taking the two sides together (fig. 16, 

 i 1 , i 2 , and i 3 ). The canines, or Hushes' (c), are present, a? 

 a rule, only in the males. The cheek-teeth (pm 2 torn 3 ), 

 or premolars and molars taken together (for there is very 

 little to distinguish them in form or size), are gene- 

 rally but six, instead of seven, on each side, above 

 and below. Here, then, is a case of specialisation by 

 suppression. One of the teeth of the ancient forms has 

 disappeared. Which is it ? The examination of a series 

 of fossil remains shows us that the first of the series 

 — the anterior premolar (jpm 1 ), a fairly large and well- 

 developed tooth in Phenacodus and Hyracotherium — 

 gradually became smaller and smaller as time advanced. 

 It is still present in Anchitherium, sometimes present 

 and sometimes absent in Hipparion. But has it entirely 

 disappeared in the modern horse ? What do we read in 

 old books on veterinary surgery ? c Wolves' teeth are 

 two very small, supplementary teeth, appearing in front 

 of the molar teeth, and supposed to have an injurious 

 effect on the eyes (!), and are, therefore, often removed 

 by farriers.' 



