Mr. Corse's Observations on the 
2 14 
formed with ridges : this however is not the case, as may be 
seen by examining a grinder just cutting the gum, (Tab. VII. 
X. and XII.) but both its sides have a fluted form, owing to 
the junction of the different strata. (Tab. VI. VIII. IX. X. 
and XI.) 
These strata, when first formed, have no firm attachment to 
each other, but always appear separate and distinct, when 
contained in their bony sockets within the jaw, after their 
membranes and soft parts are destroyed. Before any part of a 
grinder cuts the gum, there is a bony crust formed above the 
enamel, which gives a smoothness to the grinding surface. 
(Tab. VII. and XII.) 
But, after the grinders cut the gum, and the convex sur- 
face has been worn down a little by the trituration of the food, 
each lamina appears to have been formed on several points,* 
which are covered by a strong enamel. There are from 
four to eight of these points, joined together by the common 
bony matter, which fills up the space between the enamelled 
portions. 
When the grinder, however, is farther advanced in the 
mouth, its foremost laminae are gradually worn down by the 
mastication of the food; and these enamelled points or denticuli 
disappear, one after another, till the enamel, at last, runs quite 
* This appearance has been observed by Patrick Blair, M. D. F. R. S. who, 
in his Osteograpbia Elepbantina, published in 1713, calls it digitations. The above 
work, which was put into my hands by my friend Dr. Alexander Monro, junior, 
since this Paper was written, contains some useful information. The ingenious 
author had, in several particulars, a tolerable idea of the formation and structure 
of the grinders ; yet, far from suspecting a regular succession of them, he attempts 
to prove such succession to be impossible. He is equally erroneous in many other 
respects. 
