32 
COMPAEATIYE ANATOMY OF TEETH. 
gation will bring to light many other examples of this very 
peculiar method of attachment, eminently suited to, and 
hitherto only discovered in, fish of predatory habits. In the 
angler, which obtains its food by lying in ambush at the 
bottom, which it closely resembles in colour, many of the 
largest teeth are so hinged that they easily allow an object to 
pass into the mouth, but, rebounding again, oppose its egress. 
These teeth are held in position by dense fibrous ligaments 
radiating from the posterior side of their bases on to the 
subjacent bone, while the fronts of the bases of the teeth are 
free, and when the teeth are pressed towards the throat rise 
from the bone. The elasticity of the ligament is such that 
when it has been compressed by the tooth bending over 
towards it, it returns it instantly into position with a snap. 
Many of the teeth of the angler are, however, like most fishes’ 
teeth, ancliylosed firmly. The hake possesses two rows of teeth, 
the inner or shorter of which are ancliylosed, whilst the outer 
and longer are hinged. Now, the common pike possesses 
hinged teeth, whose resiliency is provided for in another way. 
Here the teeth which surround the jaws are ancliylosed by a 
development of osteodentine, which becoming continuous 
with the subjacent bone unites them to it. The manner of 
development of this is by rods of calcifying material shooting 
down through the central pulps; in the hinged teeth also 
these trabeculae shoot down and become continuous with the 
subjacent bone, only instead of rigidly ossifying they remain 
soft and elastic, so that the tooth is like an extinguisher 
fastened down by a large number of elastic strings attached 
to different points of its interior and hinged at one side. 
There are some peculiarities in the form and formation of 
elephants’ teeth which it may be interesting to notice. In 
the first place the tusks are incisor teeth, and not canines, as 
might be supposed, and they grow from persistent pulps like the 
teeth of rodents. These tusks grow to an enormous length; 
m the Indian elephant they are not so large as in the 
African species, and the tusks of the female are much 
shorter than those of the male. In the African elephant no 
such difference in size has been established. A male makes 
use of his tusk for all sorts of purposes. Thus, when a tamed 
one is given a rope to pull, he will, by way of getting a good 
purchase, pass it over one tusk and grasp it between his 
molar teeth. The tusks of the Siberian mammoth, whose 
remains are abundant, are strongly curved, and attain the 
length of 18ft., and a weight of 2001b. each. A pair of 
African tusks exhibited at the Great Exhibition of 1851 
weighed 3251b., and measured 8ft. Gin. in length, and 22in. 
in circumference, but the average tusks imported from Africa 
