219 
different Species of Asiatic Elephants. 
way through the alveoli, and cut the gum, as they advance for- 
ward in the jaw. The grinding surface has rather a concave 
form, to adapt itself to that of the grinder in the upper jaw. 
The number of layers does not always correspond with those 
of the grinder in the upper jaw ; but, like them, consists of 
from four to about twenty-three teeth or laminae. (Tab. VI. 
and XI.) 
In both jaws, the alveoli are firmly attached, anteriorly and 
laterally, to the bony plates of which the jaw is composed ; but, 
at the posterior part, these alveoli are separate from the jaw, 
and have only a membranous attachment. The alveoli termi- 
nate in an apex or point, (Tab. VII. IX. X. and XI.) and be- 
come thicker and stronger, (Tab. VI. IX. and XI.) as the ele- 
phant advances in years. 
In the lower jaw, the portion of the alveolus which is attached 
to the inner plate, is thick and spongy; and, through the under 
part of this spongy substance, there is a pretty large foramen, 
for transmitting the blood-vessels and nerves which supply the 
teeth and lower jaw. The alveolus of the grinder advances in 
the same manner in the lower as in the upper jaw; and, as the 
fangs are absorbed, it is absorbed also. 
In proportion as the fangs or roots are added to the grinder, 
it rises through the alveolus, and cuts the gum ; at the same 
time, the bottom of the alveolus, in which the grinder is formed, 
becomes more spongy, and shoots up between the fangs, firmly 
embracing them, and thus preventing the grinder from being 
shaken or disturbed by the trituration of the food. (Tab. VI„ 
VII. and XI.) 
As the grinders of the upper and under jaws wear away, the 
roots of them are lengthened, and become more solid, by the 
