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the direction of the worm of the screw, or of the cutting end of the auger, or the shape of other tools or instruments-is not arbitrary, but has relation to a natural endowment of the body. He who is left-handed is most sensible to the advantages of this arrangements, whether in opening the parlour-door, or a penknife. On the whole, the preference of the right hand is not the effect of habit, but is a natural provision, and is bestowed for a very obvious purpose: and the property does not depend on the peculiar distribution of the arteries of the arm-the preference is given to the right foot, as well as to the right hand.*
THE SUBSTITUTION OF OTHER ORGANS FOR THE HAND.
AFTER having examined how one instrument, the hand, is modified and adapted to a variety of uses in different animals, it only remains, for elucidating the subject further, to contrast the hand with its imperfect substitutes in other creatures. From the insect tribe, I might have derived some of the most curious examples of instruments suited for purposes similar to those of the hand and fingers of man; but I have intentionally confined the inquiry to the higher classes of animals.
The habits of certain fishes require that they should cling firmly to the rocks, or to whatever is presented to them as a means of support. Their locomotive powers are perfect; but how do they become stationary in the tide or stream? For example, I have often thought it wonderful that the salmon or trout should keep its place, night and day, in the rapid current.
[The poising and motion of fishes in the water has interested some of our greatest philosophers, as Galileo and Borelli. It is estimated that fishes make their way through a medium which resists nine hundred times more than the atmosphere: but then, as it offers a certain resistance to their progress, it resists also the motion of their tail and fins by which they have their power of progression. The breadth of the tail of fishes, compared with that of their fins, and its muscularity and power, declare what is affirmed to us upon authority-that the tail is the great instrument of their progression; and we can see that when the trout darts away, the force of his motion lays down the fins close upon his body. But the fins direct him, as out-riggers, and the pectoral fins especially, by raising or depressing the head, give direction to the whole body under the force of the tail. The lateral fins, and particularly the pectoral fins, also sustain him in the right position in the water: without the co
operation of these with the tail, the fish would move like a boat sculled by one oar at the stern. As the digestion of fishes, as well as that of other animals, is attended with the extrication of air, and as the intestines are below the centre, the belly would be turned up but for the action of these lateral fins; as we see takes place in a dead fish. The tail and fins are the instruments of motion; but the incessant action of the muscles which move these is a just matter of admiration. If a fish move with his head down the stream, he must move more rapidly than the water, or the water gets under the operculum of the gills, and chokes him. He lies, therefore, continually with his head to the stream. We may see a trout lying for hours stationary, whilst the stream is running past him; and they seem to remain so for days and nights. In salmon-fishing, the fly is played upon the broken water, in the midst of the torrent; and there the fish shows himself rising from a part of the river where men could not preserve their footing, though assisted by poles, or by locking their arms together. When the salmon leaps, he makes extraordinary exertions. Just under the cataract, and against the stream, he will rush for some yards, and rise out of the spray six or eight feet; and amidst the noise of the water, they may be heard striking against the rock with a sound like the clapping of the hands. If they find a temporary lodgment on the shelving rock, they lie quivering and preparing for another somerset, until they reach the top of the cataract. This exhibits not only the power of their muscles, assisted by the elasticity of their bones, but the force of instinct by which they are led to seek the shallow streams for depositing their eggs. The porpoise will sail round and round a ship which is sailing at fourteen miles an hour: a thing almost as surprising as the fly circling round the horse's ear for a whole stage. To all this may be added, that the solid which mathematicians have discovered, by refined application of the calculus, and have termed "the solid of least resistance," because it is the conformation which is less than any other affected by the resistance of any medium, resembles a fish in its form.* The sea varies in temperature and pressure at different depths, and no doubt the texture of the fish, and especially of its integument, must conform
* According to Lacepede, the speed of a salmon is about twenty-six feet in a second.
to this variety. The swimming-bladder is the means of adjustment by which the fish lives at its native depths without waste of animal exertion: such is the power of expansion of the airbladder when relieved from the pressure, that, when a fish is brought up from the greatest depth, it inverts and thrusts out the viscera from the mouth. We do not see, however, that naturalists have adverted to the place of this swimming-bladder. It lies close to the spine, and appears to counterbalance, in some measure at least, the air in the intestines by being thus placed above them. In the Cetacea, as the whale, their buoyancy proceeds from the quantity of oil under the skin, especially of their head, and which it has been observed is bestowed in order to insure their readily coming to the surface to breathe when their natural powers are weakened. For the same reason, that they may raise their heads to the surface, their tails are horizontal. In the jelly-fish, those soft animals which float in sheltered estuaries (the physsophora), there is an air-vessel which they can fill and empty, by which means they rise or sink at pleasure. Others (the villela) raise a sail. Some of this class propel themselves by taking in water, and suddenly rejecting it.]*
In the sea, some fishes are provided with special means of clinging to the rocks. The lump-fish (cyclopterus lumpus) fastens itself by an apparatus on the lower part of its body; while the sucking-fish (remora) has a similar provision on its back, by which it attaches itself to the shark, or to whatever is afloat, as the bottoms of ships: and it was from the ancients believing that this fish was able to stop a ship under sail, that Pliny called it remora. We must admire the means by which these fishes can retain their proper position in the water, without having to cling either by their fins or their teeth, or being prevented from catching their food. The apparatus resembles a boy's sucker: the organ is pressed against the surface to which the creature is about to fix itself, the centre is then drawn upon by muscles, in the same manner as the sucker is drawn by the cord, and thus a vacuum is made. Dr Shaw tells us, that on throwing a lump-fish into a pail of water, it fixed itself so firmly to the bottom, that when he took hold of it by
*Author's note, in edition of illustrative notes by Lord Brougham "Paley's Natural Theology, with and Sir Charles Bell."
the tail, he could lift the pail off the ground, although it contained some gallons of water.*
In the cuttle-fish we see a modification of the same kind of apparatus: the suckers are ranged in rows along the lower part of their feelers or arms, so as to become instruments of prehension and of locomotion. They can be turned by the animal in any direction, either to fix itself, or to drag itself from place to place. In the Indian seas these creatures become truly formidable, both from the length of their arms, which extend to eight or nine feet, and from the tenacity with which they cling.t
There is another fish, which, from its name, we should expect to be able to perform strange antics; it is called the "harlequin angler." The appearance of the fish is grotesque and singular;