The general form of the whale, notwithstanding its position among the Mammalia, is similar to that of the fishes, and the horizontal elongation of the body, the smooth and rounded surface, the gradual attenuation of the extremities of the trunk, and the magnitude of the fins and tail, are specially adapted to easy and swift motion in the water. The arrangement of the bones composing the anterior limb is very curious. The whole of the fin consists of exactly the same parts as those which we find in the human hand and arm; but they are so concealed beneath the thick cutaneous or integumentary envelope, that not a trace of bone is visible. In this respect an intermediate organization is shown by the fore limbs of the seal.
The posterior extremity, in all the Cetacea, is either absolutely deficient, or else rudimentary. If rudimentary, its sole vestige consists of certain small bones, the imperfect representation of a pelvis, suspended, as it were, in the flesh, and unconnected with the spinal column. Here we may observe a remarkable difference between the whale and the seal: in the latter, as we have seen, there is a short tail, and the posterior extremities perform the office of a true caudal fin; in the former this important organ of progression consists, to use Mr. Bell’s words, of “an extremely broad and powerful horizontal disc, varying in figure in the different genera, but in all constituting the principal instrument of locomotion.” In fishes the tail is set vertically, but in whales horizontally; and it has been well said that the admirable adaptation of such a peculiarity in its position to the requirements of the animal forms a fresh and beautiful illustration of the infinite resource and foresight of the Creative Wisdom.
Thus: the fishes, respiring only the air contained in the dense liquid medium in which they live, require no access to the atmosphere; and, therefore, their progression is chiefly confined to the same region. But the whales, breathing atmospheric air, must necessarily come to the surface for each respiration; and hence they need a powerful instrument or lever, the position of which shall apply its impulse in a vertical direction, so as to impel their colossal bulk from the lowest depths of ocean to the surface every time the lungs require to receive a fresh supply of atmospheric air. The greatest rapidity of motion is effected by alternate strokes of the tail against the water, upwards and downwards; but the usual progression is accomplished by an oblique lateral and downward impulse, first on one side and then on the other, just as a boat is propelled by a man with a single oar in the art of “sculling.” The extent of the tail in some of the larger species is really immense; the superficies being no less than about a hundred square feet, and its breadth considerably exceeding twenty feet.
The common, right, or Greenland whale (Balæna mysticetus) has been, for centuries, the object of man’s systematic pursuit, on account of its valuable oil and scarcely less valuable baleen.
THE GREENLAND WHALE.
This whale seldom exceeds fifty to sixty feet in length, or thirty to forty in girth, and, therefore, is by no means the head of its family. As in other species, the body is thick and bulky forwards, largest about the middle, and tapers suddenly towards the tail. The head is colossal; broad, flat, and rounded beneath, and narrow above; it forms about a third of the animal’s entire length, and is about ten or twelve feet broad. Its lips—such lips!—are five or six feet thick. They do not cover any teeth, but they protect a pair of very formidable jaws. The cavernous interior of the mouth is filled up with two series of whalebone laminæ, about three hundred in each, which require particular description. The whalebone, or baleen, as it is called, consists of numerous parallel plates, layers, or laminæ, each of which is formed of a central coarse fibrous layer lying between two that are compact and externally polished. But this outer part does not completely cover the inner; a kind of edge is exposed, and this edge terminates in a loose fringed or fibrous extremity. Moreover, at the base of each plate of baleen lies a conical cavity, covering a pulp which corresponds with it; and this pulp is sunk within the substance of the gum or buccal membrane stretched over the palate and upper jaw.
The compact outer layers of the baleen plate are continuous with a white horny layer of the gum, which passes on to the surface of each plate; and the pulp may be regarded, therefore, as the secreting organ of the internal coarse structure only. The filaments of the fringe are exceedingly numerous, and so fill up the mouth-cavity as to form a very efficient and ingenious sieve or strainer; and as the esophagus, or “swallow,” of the whale is so confined as to be unable to admit of the passage even of the smaller fish, and the food of the whale consequently is limited to minute organisms, such as the medusæ, this skilfully devised construction is absolutely requisite in order to retain the whole of those which are taken into the mouth.
The mode in which the whale feeds may be thus described:—
The broad waters of the Arctic seas teem with innumerable shoals of molluscous, radiate, and crustaceous animals, and these are frequently so numerous as absolutely to colour the wave-surface.