CETACEANS. 
105 
Their external form is fish-like, the body being fusiform or 
spindle-shaped, passing anteriorly into the head, usually without 
any distinct constriction or neck, and posteriorly tapering off 
gradually towards the extremity of the tail, which is provided with 
a pair of lateral, pointed expansions of skin supported by dense 
fibrous tissue, called “fiukes,^^ forming together a horizontally- 
placed triangular propelling organ, notched in the middle line 
behind, with which the animals scull themselves through the water. 
The characteristic form of the tail is well seen in many of the smaller 
stuffed specimens in the Gallery, and in that preserved and attached 
to the great skeleton of the Rorqual, to be spoken of presently. 
The head is generally large, in some species attaining to even 
more than one third of the entire length of the animal, and the 
aperture of the mouth is always wide, and bounded by stiff 
immobile lips. The fore limbs are reduced to the condition of 
fiattened paddles, encased in a continuous skin, showing no ex- 
ternal sign of division into arm, forearm, and hand, or of separate 
fingers, and without any trace of nails. There are no signs of hind 
limbs visible externally. The general surface of the skin is smooth 
and glistening, and devoid of hair, although in most species the 
mammalian character of hairiness is just indicated by the pre- 
sence of a few fine bristles in the neighbourhood of the mouth, 
which either remain through life, or are to be found only in the 
young state. Immediately beneath the skin, and intimately con- 
nected with it, is a thick layer of fat, held together by a dense 
mesh of fibrous tissue, constituting the blubber/^ which serves 
the purpose of the hairy covering of other mammals in retaining 
the heat of the body. In nearly all species there is a fin, more 
or less triangular in shape, composed only of skin and fibrous 
tissue, near the middle of the back, which, as in the analogous 
dorsal fin of fishes, assists to keep the animal in an upright posi- 
tion when swimming through the water. The eye is small ; and 
the aperture of the organ of hearing extremely minute, and with- 
out vestige of a pinna or external ear. The nostrils, generally 
called blowholes,^^ open separately, or by a single valvular 
aperture, not (except in the Sperm Whale) at the extremity of 
the snout, but near the top of the head. 
The bones generally are spongy in texture, their cavities being 
