252 Mr. Home’s Observations on the Structure of 
substance in the middle of the tooth, as in the horse, in shape 
of crescents, and a very small portion in the hollows on the 
outside of the circumference of the tooth; but none on the pro- 
jecting parts. 
In the grinding teeth of the sheep, the middle portions of 
bone are similar to those of the cow, but on a much smaller 
scale ; there is no portion of bone on the outside of the tooth. 
It is not to be wondered at, that there is so great a variety in 
the grinding surfaces of the teeth of different genera of grami- 
nivorous quadrupeds, each, no doubt, adapted to the kind of food 
they are in a state of nature destined to live upon, since there is 
even a variation between the teeth of the African and Asiatic 
elephants. In the African elephant, the processes of which the 
tooth is composed are not flattened ovals, as they have been 
described in the Asiatic, but are in the form of an oblong square 
or parallelopipedon, so that, in the middle line of the tooth, the 
processes are in contact with each other, although at no other 
part ; by this means, the middle line of the tooth is the hardest ; 
the whole surface therefore does not wear regularly, as in the 
Asiatic elephant, but with a ridge in the middle. 
As a description of the grinding surface of the teeth of the 
African elephant, the horse, cow, and sheep, would be very 
tedious, to make it at all intelligible, and as the surfaces of the 
teeth can be very distinctly represented in a drawing, I have 
preferred that mode of showing their comparative structure. 
See Tab. XVI. and XX. 
Having, by the foregoing observations, established a well 
marked characteristic distinction between the teeth of truly 
carnivorous and truly graminivorous quadrupeds, I was desirous 
