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 
bemg 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 bemg 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 
