24 CETACEANS. 
THE SPERM- WHALE. 
Genus Physeter. 
The sperm-whale, or, as it is frequently called from its French title, cachalot 
(Physeter macrocephalus), is one of the largest of the Cetaceans, fully rivalling in 
size the Greenland whale. As with many other species, its dimensions have, how- 
ever, been considerably exaggerated ; although, on the other hand, it is quite probable 
that when the species was more abundant than at present, some individuals attained 
a size which is now never reached. Be this as it may, the male sperm-whale is 
definitely known to attain a length of from 55 to 60 feet; but females are said not 
to reach much more than half these dimensions, while their form is proportionately 
more slender. The essential generic characteristics of the sperm-whale are to be 
found in the great proportionate size of the head, which equals about one-fourth of 

SKELETON OF SPERM-WHALE, 
the total length of the animal, and in the number of the teeth being from twenty to 
twenty-five on each side of the lower jaw. 
In appearance the sperm-whale is ungainly and ugly in the 
extreme, this being chiefly due to the great height and abrupt trunca- 
tion of the enormous muzzle, upon the summit of which is situated the S-shaped 
aperture of the nostrils, somewhat to the left of the middle line. The mouth, which 
is of great length and capacity, opens below, and at some distance behind the 
extremity of the muzzle. On the upper surface of the skull, as seen in our figure 
of the skeleton, is a huge cavity, bounded behind by a tall vertical wall of bone ; 
this cavity being filled in the living animal with the substance known as spermaceti, 
of which more anon. In front of this hollow protrudes the long rostrum of the 
upper jaw; the gum of which contains rudimentary teeth. The lower jaw is very 
long and slender; its two branches being united in the middle line for about half 
their total length. The teeth are implanted in the lower jaw in a long groove, 
partially divided into sockets by incomplete bony partitions. These teeth are of 
large size, and, when unworn, are pointed and recurved at their tips. They are 
composed solely of ivory, and the pulp-cavity at their base remains open for a long 
period, although generally more or less completely closed in adult life, when the 
whole base of the tooth becomes much flattened from side to side. The tongue and 
interior of the mouth are of a glistening white colour; and the diameter of the 
throat is very large. The eye is placed somewhat above the angle of the mouth, 
and a short distance behind it is the minute aperture of the ear, which is said not 
to exceed a quarter of an inch in diameter, 
Form. 
