THE DECIDUOUS DENTITION 241 



tachment areas of the masticatory muscles and to the fulcrum, 

 that is to say to the temporo-manclibular articulation, are the 

 teeth in the best situation for exerting pressure and are molari- 

 form whereas those teeth furthest removed from muscle at- 

 tachments and joint are best placed for swift movement and 

 cutting or piercing action and are simple chisel-like (incisors) 

 or conical (canines) in shape. Intermediate in position are the 

 premolars which are also intermediate in function.* In the 

 milk dentition the relative shortness of the jaws is associated 

 with fewer' teeth: those forms of teeth naturally are found 

 which are most essential to the animal's existence. Hence the 

 milk postcanines in Man and the Anthropoids reproduce the 

 more fundamental features of the cheek teeth as a series in the 

 permanent dentition. 



This suggestion calls at once for study of the milk teeth that 

 we may find out what are the more essential features of the 

 human and Anthropoid dentitions. It brings home to us the 

 fact that neither of the terms milk molars and milk premolars 

 accurately defines the characters of the deciduous postcanine 

 teeth. 



The milk dentition of Man, of all Anthropoids and Old- 

 World Apes is: 



2 12 

 i — , c —, m— . total 20. 



We shall take as our first example the milk dentition of the 

 European (Figs. 85, 86). 



Apart from smallness of size the deciduous teeth possess 

 enamel of a different hue from that of the permanent teeth. 

 The neck is relatively better marked, the crown being more 

 globular and in the case of the molars the roots more diver- 

 gent than in the successional teeth. As to the incisors which 

 are quite vertically situated in the jaws the relationship in size 



*This interpretation must not be expected to fit all facts. For example in the very 

 specialized Horse the premolars are all completely molariform in appearance though 

 their relation to muscular attachments and joint is not closer than in Mammals with 

 less complex premolars. 



