ANATOMY AND PHYSIOLOGY OF ('ETACEOUS ANIMALS.
is: their general form, these animals nearly resemble the ordinary tribes of fishes, and like these, are enabled, by ;hei• conformation, to move through the water with great veloc ity. In most species the head is conical, and more or less pointed at the snout ; though the great spermace:i whale, and some others of the Myselfr genus, arc an exception to this general rule. In most of them the head is extremely large, in proportion to the body, and swells out at the sides towards the insertion of the lower jaw. The head is joined to the body by a neck, so short, as to be scarcely perceptible. There is no appearance of extern?' ear, hut only a small of ifice, leading to the internal organ of hearing. The eyes arc, in gen • al, extremely small. in proportion to the size of the anim, t. and arc commonly situated vets fix back, near the ai ti ciliation of the low( r jaw. There is always one hole. and in some species two holes, opening in sonic part of the top of the head, and serving less for nostrils than for ejecting the water taken in by the animal's mouth.
The body is more or less conical or et lindrical. entire ly without hair, and covered with a thick and dense cuti cle. At the posterior or sacral extremity, the body te urinates in a forked tail, that is flattened horizontally, and is very strong and muscular. In some species there is a fin, in others a protuberance, on the top of the back, and all of them have two members, one on each side of the chest, which are usually denominated pectoral fins, but are better entitled to the name of swimming paws, as they nearly resemble the atlantal extremities, or fore feet of seals and walrusses. These animals have evident external organs of reproduction, and in the males espe cially these are sometimes very large and prominent.
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The motive organs of eetaceous animals have many striking peculiarities. The skeleton has its parts joined together in such a manner, and is so deeply imbedded within the fat and muscles, that it does not, as in quad rupeds, much influence or discriminate the external form of the animal. The bones have a very loose and coarse texture, so that the fibres are readily distinguish ed, even on a superficial view ; and in some, as the jaw and ribs, easily loosened, and rendered extremely obvi ous by maceration. None of the bones have any medul lary cavity. Though the neck in these animals appears extremely short externally, that part of the skeleton is composed of the same number of bones as in quadrupeds, namely seven ; though in some of them, as the dolphin and norpesse, the two next the head, and in others, as the several species of fzhyseter, the six last, or sacral vertebra', are united or anchyloscd. Thus in the two former species, there can be no rotatory motion between the head and neck; and in the physetcr tribe, the motions of the head must he exceedingly obscure. The number
of joints composing the back differs considerably in these animals. Some, as the do//zhin and porpesse, have thirteen ; others, as the only twelve. The number of ribs also varies, depending on that of the dor sal vertebrae. In some species Alr John Hunter distin guished eighteen ribs on each side ; while in some sper maceti whales, thrown ashore on the coast of France, there were only eight ribs on a side.
There is no pelvis in the skeleton of these animals, and it is therefore impossible to distinguish the lumbar vcriebric from those of the coccyx or tail. In many spe cies, these sacral or posterior vertebrae arc very numerous. Thus, in the dolphin and porpcsse, they exceed fifty. The most remarkable part of the skeleton of cetaceous animals is, the atlantal extremities or swinzming paws, whose hones in number and articulation nearly resemble those of man. We can clearly distinguish a scapula or blade bone, an humerus or shoulder-bone, two bones si milar to those of the fore-arm, and a hand consisting of live lingers. All these bones arc, however, much flat tened, and susceptible of but little motion on each other; though they are so connected by means of cartilage, that the whole number possesses considerable pliability and power of general motion.
The flesh which covers the skeleton is of a red colour, and nearly resembles that of the horse and cow. It is in general hard, lirm, dry, and tendinous. The muscles of these animals soon lose their librous texture after death, speedily running into putrefaction ; though this change is apparent, more from the change of texture, than from the disagreeable odour which the flesh exhales. 'The most remarkable part of the muscular system is that which gives motion to the tail. This organ is emnposed of two oval lobes, formed of three layers of tendinous fibres, of which the two external or peripheral layers have a direction similar to that of the lobes, and are crossed by those of the internal or central layers. By means of this structure, the tail in these animals is sus ceptible of very extensive and rapid motion, and not only serves the purpose of a fin, to impel the animal forwards, but furnishes him with a most formidable and effectual offensive weapon. Indeed the force of the tail, in the larger species, where it sometimes measures above 20 feet from the tip of one lobe to that of the other, is so great, that a single stroke with it, well aimed, is suffi cient to cut a boat in two, or sink it to the bottom.
When we consider the enormous bulk of some spe cies of whales, we shall be surprised at the celerity with which they make way through the water. It is com puted by the French naturalists, that some of them are capable of rushing through 33 feet in a second of time, and that, supposing them to move with a uniform and uninterrupted motion, 23 days would be sufficient for enabling them to circumnavigate the globe.