But the arm, which in man moves freely, is here chained to the body as far as the hand, and the latter, which, in obedience to human volition and intellect, executes such miracles of industry and art, is here covered with a thick skin, and appears as a broad undivided fin or flapper. Yet still it is destined for higher service than that of a mere propelling oar, as it serves the mother to guide and shield her young. The lower extremities are of course wanting, but their functions are performed by the mighty horizontal tail, by whose powerful strokes the unwieldy animal glides rapidly through the waters.
The cetaceans distinguish themselves, moreover, from the fishes by the bringing forth of living young, by a greater quantity of blood, by the smoothness of their skin, under which is found a thick layer of fat, and by their simple or double blow-hole, which is situated at the top of the head, and corresponds to the nostrils of the quadrupeds, though not for the purpose of smelling, but merely as an organ of respiration.
Bones of the Anterior Fin of a Whale.
Our knowledge of the cetaceans is still very incomplete; and this is not to be wondered at, when we consider that they chiefly dwell in the most inaccessible parts of the ocean, and that when met with, the swiftness of their movements rarely allows more than a flighty view of their external form. Thus their habits and mode of living are mostly enveloped in obscurity; and while doubtless many cetaceans are to the present day unknown, one and the same species has not seldom been described under different names, to the no small confusion of the naturalist.
The cetaceans are either without a dental apparatus, or provided with teeth. The former, or the whalebone whales, have two blow-holes on the top of the head, in the form of two longitudinal fissures; while in the latter, (sperm-whales, unicorn-fish, dolphins,) which comprise by far the greater number of species, there is but one transversal spout-hole. In all whales the larynx is continued to the spouting canal, and deeply inserted or closely imbricated within its tube. Thus no tones approaching to a voice can be emitted except through the spiracles, which are encumbered with valves, and evidently badly adapted for the transmission of sound. Scoresby assures us that the Greenland whale has no voice, and Bennett frequently noticed sperm-whales suffering from extreme alarm and injury, but never heard any sound from them beyond that attending an ordinary respiration.
The whalebone whales are either smooth-backs (Balænæ), or fin-backs (Balænopteræ), having a vertical fin rising from the lower part of the back. To the former belongs the mighty Greenland Whale (Balæna mysticetus), the most bulky of living animals, and of all cetaceans the most useful and important to man. Its greatest length, according to Scoresby, is from sixty to seventy feet, and round the thickest part of its body it measures from thirty to forty feet, but the incessant persecutions to which it is subjected scarcely ever allow it to attain its full growth.
The whale being somewhat lighter than the medium in which it swims, its weight may be ascertained with tolerable accuracy; and Scoresby tells us that a stout animal of sixty feet weighs about seventy tons, allowing thirty to the blubber, eight or ten to the bones, and thirty or thirty-two to the carcase. The lightness of the whale, which enables it to keep its crown, in which the blow-hole is situated, and a considerable extent of back above the water, without any effort or motion, is not only owing to its prodigious case of fat, but also to the lightness of its bones, most of which are very porous and contain large quantities of fine oil; an admirable provision of nature for the wants of a creature destined to breathe the atmospheric air, and to skim its food from the surface of the waters.
The unsightly animal shows disproportion in all its organs. While the tail fin measures twenty-four feet across, the pectoral fins or paddles are no more than six feet long. The monstrous head forms about the third of the whole body, and is furnished with an equally monstrous mouth, which on opening exhibits a cavity about the size of an ordinary ship's cabin. The leviathans of the dry land, the elephant, the rhinoceros, and the hippopotamus, are provided with tusks and teeth corresponding to their size—huge weapons fit for eradicating trees or crushing the bone-harnessed crocodile; but the masticatory implements of the giant of the seas are scarcely capable of dividing the smallest food. Instead of teeth, its enormous upper jaw is beset with about 500 laminæ of whalebone, ranged side by side, two-thirds of an inch apart, the thickness of blade included, and resembling a frame of saws in a saw-mill. Their interior edges are covered with fringes of hair; externally they are curved and flattened down, so as to present a smooth surface to the lips. The largest laminæ, situated on both sides of the jaw, attain a length of fifteen feet, and measure from twelve to fifteen inches at their base; in front and towards the back of the mouth they are much shorter.
