THE ROOTS OF TEETH 261 



obviously single but not primitively so: rather it represents the 

 fused roots of the primitive tooth uncompleted at the apex. 

 In the Horse it is only in old age that the divergent root tips 

 appear. Completely hypsodont teeth possess roots of persistent 

 growth and such have already been observed in advanced 

 forms of incisors and molars alike. 



It is especially striking that in the Horse which is an example 

 of extreme hypsodonty the milk dentition even today is less 

 high-crowned, thus confirming the view just put forward that 

 the brachyodont type with two or more roots is primitive. 



From lack of space it is impossible to deal adequately witli 

 the tooth roots in all orders but a little attention to the appear- 

 ances found in the higher Apes and in Man will not be mis- 

 placed. 



The first feature which strikes the observer in comparing 

 the teeth of an Anthropoid with those of Man is the fact that 

 each of the upper premolars possesses three roots like the 

 molars. Three roots are occasionally found in the human 

 upper premolars; in fact I am inclined to believe that this 

 condition is not so rare as is said to be the case. The bifid or 

 three-pointed tip and the grooving of the root are indications 

 of a former separation into more than one fang. Both in 

 Anthropoids and in Man grooving of the root of the canine 

 and of the incisors occurs, in the former more frequently than 

 in the latter. These features and in addition the clearly marked 

 separate roots of non-persistent growth so characteristic of all 

 Primate teeth with one exception are certain evidence of the 

 retention of fairly primitive root features in this order. 



The skiagram of a jaw in which the permanent teeth are 

 still developing focuses attention upon the situation of the 

 canine rudiment. This lies much more remote from the gum 

 t^ian any of the other rudiments (see Fig. 86). In the great 

 Anthropoids we have already noted that date of eruption of 

 the canine varies with sex. In the female Chimpanzee it 

 erupts before the third molar but in the male it is the last 

 tooth to come into place. In both cases the canine erupts 



