ELEPHAS PRIMIGENIUS. 229 



by that part of the complex grinder which was concealed in 

 the closed recess of the socket, and which part, in the 

 present instance, is folded upwards and laterally upon the 

 concave side of the tooth ; the sides of the digitated plates 

 being parallel with the grinding surface of the tooth. 



There are few examples of natural structures that mani- 

 fest a more striking adaptation of a highly complex and 

 beautiful structure to the exigences of the animal en- 

 dowed with it, than the grinding teeth of the Elephant. 

 Thus the jaw is not encumbered with the whole weight of 

 the massive tooth at once, but it is formed by degrees as it 

 is required ; the subdivision of the crown into a number of 

 successive plates, and of the plates into subcylindrical pro- 

 cesses, presenting the conditions most favourable to pro- 

 gressive formation. But a more important advantage is 

 gained by this subdivision of the grinder : each part is 

 formed like a perfect tooth, having a body of dentine, 

 a coat of enamel, and an outer investment of cement ; 

 a single digital process may be compared to the simple 

 tooth of a Carnivore ; a transverse row of these, therefore, 

 when the work of mastication has commenced, presents, 

 by virtue of the different densities of their constituent 

 substances, a series of cylindrical ridges of enamel, with 

 as many depressions of dentine, and deeper external valleys 

 of cement : the more advanced and more abraded part of 

 the crown is traversed by the transverse ridges of the 

 enamel investing the plates, inclosing the depressed surface 

 of the dentine, and separated by the deeper channels of the 

 cement : the fore-part of the tooth exhibits its least effici- 

 ent condition for mastication, the inequalities of the grind- 

 ing surface being reduced in proportion as the enamel and 

 cement which invested the dentinal plates have been worn 

 away. This part of the tooth is, however, still fitted for 



