322 Mr. Home's Observations on the grinding Teeth 
As soon as the sixth grinder has cut the gum, a new cell 
begins to appear immediately beyond it, to receive the rudiments 
of another tooth. 
This last cell, at seven years of age, is very small ; and 
the specimens in my possession do not enable me to prose- 
cute the enquiry ; but there is every reason to believe the tooth 
formed in it, equals or exceeds the large one that has been 
described. 
The appearances which have been mentioned will be better 
understood by referring to the annexed figures, (Plates XX, 
XXI, XXII, and XXIII.) than by any verbal description. 
The large grinder in the wild boar resembles those of the Sus 
Ethiopicus and elephant, in having a larger extent of masti- 
cating surface than is met with in other teeth ; it differs, how- 
ever, materially in its structure, having that surface composed 
of a strong crust of enamel, with projecting transverse ridges ; 
showing that it is not intended for grinding simply, but belongs 
to an animal which, like the human species, is fitted to live on 
both animal and vegetable substances. 
Previous to a tooth of this structure having been discovered 
with an extended masticating surface, the curious mechanism 
of the elephant's grinders appeared to be the only one peculiarly 
fitted for that purpose ; but we now find, that the more usual 
structure of grinding teeth will admit their surfaces to be 
extended, whenever their enlargement becomes necessary to 
enable the animal to prepare the food for the process of 
digestion. 
The elephant, the ; Sus Ethiopicus, and the wild boar, are the 
only recent animals in which this extended masticating surface 
of the grinding teeth has been met with. There is nothing 
