COMPAEATIVE ANATOMY OF TEETH. 
33 
do not exceed 201b. to 501b. in weight. Indian elephants 
seldom have tusks attaining very large dimensions. One was, 
however, shot by Sir Victor Brooke with a tusk 8ft. long, 
weighing 901b. The female elephant’s tusk is liable to the 
attacks of a dipterous insect, which imbeds itself in the gums, 
and either gnaws off the ivory in a circle or the ivory is 
absorbed owing to the irritation set up by the insect. The 
tusks of the elephant are implanted in long and stout 
sockets, and grow from persistent pulps throughout the life¬ 
time of the animal. 
Some curious examples of spear heads and bullets found 
in the centre of tusks exist. In these cases the missile has 
penetrated into the pulp cavity, where the bone is thin. The 
ivory has grown around it, and, increasing in length, the 
tusk has carried the iron forward, which, when the tusk has 
been cut up by the turner, has been discovered. In the museum 
of the Odontological Society is the head of a spear, measuring 
7J by 1^ inches, so embedded. In 1879. there were 9,414cwt. 
of ivory, of the value of £406,927, imported into this country. 
Though the elephant has during the course of its life 24 
molars, they are not all in place, nor, indeed, are they all 
actually in existence at the same time. Only one whole 
tooth on each side or portions of two when the front one is 
nearly worn out, are in use at the same time. After a tooth 
has been in use for some time and is worn down, a new tooth 
comes up to take its place behind it, and absorption in the 
old tooth being set up, it is shed off, and a new tooth pushes 
up into its place. Each successive tooth is of greater size 
than its predecessor ; thus in the Indian elephant the first 
tooth has, on an average, 4 transverse plates, the second has 
8, the third 12, the fourth 12, the fifth 16, the sixth 24 to 27. 
In the African elephant, in which the individual plates are 
much broader, they are fewer in number. 
Of course, everyone will have noticed that in the grinders 
of the horse or cow the enamel does not surround the tooth, 
as in our teeth, but that it runs into the tooth substance in a 
peculiar manner, yet constant in its devious path. There is 
a wonderful evidence of design in this. If you took a piece of 
wood, however rough and hard at first, and made a rub-stone 
of it, in time its surface would be worn even and smooth 
—the harder the wood the smoother and more polished 
would it become. But if you were to place, first a layer 
of boxwood, then a layer of steel, and then a layer of 
deal side by side, and screw them into a solid block and 
use it as a rub-stone, your deal and boxwood would wear 
away before your steel, and your rub-stone would remain 
rough. Now, in the elephant, which chews an immense 
