XVII 
THE CROCODILE 
217 
fairly constant in a given species. Sixty-eight or 
seventy teeth is not an uncommon number for a croco¬ 
dile of the Nile. In some species of these reptiles the 
teeth interlock as thoroughly as the teeth of a rat-trap ; 
in others the interlocking is not so complete, but they 
are very efficient, for the strength of the teeth and jaws 
of crocodiles is such that they rarely let go any animal 
that is fairly seized. 
The teeth are conical—somewhat compressed from 
side to side—which gives them sharp edges : they vary 
much in size, and the fourth in the lower (mandibular) 
set is so constantly larger than the teeth immediately 
adjacent that it is sometimes termed the canine tooth. 
This long tooth fits into a notch in the side of the upper 
jaw. The teeth ’ consist of dentine, capped by enamel, 
and the roots have a coating of cementum. 
Crocodiles shed their teeth throughout life, but they 
are quickly replaced. The method of replacement is 
after this fashion :—The young tooth grows on the 
median side of the functional tooth ; as the new tooth 
increases in size the adjacent wall of the root of its pre¬ 
decessor is absorbed. Eventually the new tooth is found 
within the pulp cavity of the one it is destined to replace. 
In due course the persistent growth of the young tooth 
pushes the old one out, and takes its place : when this 
happens a new tooth has started to supplant it in 
turn. 
A newly-cut tooth has a sharp point: by use the 
point is worn down, but the edges are retained ; coinci¬ 
dent with the wear of the crown, erosion takes place at 
the margin of the enamel-cap and a definite groove forms 
around the tpoth, dividing it into a crown, neck, and root. 
This is only seen in old teeth. Sometimes the crown of 
an old tooth has facets due to wear. 
The digestive organs of crocodiles are very powerful. 
Birds, small mammals and portions of large animals are 
retained in a wide and capacious gullet until the stomach 
is ready to receive them. 
