. Cassell's natural history. Animals; Animal behavior. no IF THE GOEILLA CLIMBS. 25 most unleurned in anatomy neetl only be reminded that muscles are adherent to certain parts of bones. The bone, by itself, is motionless, and the force which can move it, and with it, the surrounding fle,sh and skin, acts thi-ough the muscles, and these consist of vast numbers of long microscopic fibrils, placed side by side, and adherent, at both ends, to different bones. The fibrils have a vast amount of energy in them, and they can contract, or, in other words, shorten; the diminution in length being accompa
. Cassell's natural history. Animals; Animal behavior. no IF THE GOEILLA CLIMBS. 25 most unleurned in anatomy neetl only be reminded that muscles are adherent to certain parts of bones. The bone, by itself, is motionless, and the force which can move it, and with it, the surrounding fle,sh and skin, acts thi-ough the muscles, and these consist of vast numbers of long microscopic fibrils, placed side by side, and adherent, at both ends, to different bones. The fibrils have a vast amount of energy in them, and they can contract, or, in other words, shorten; the diminution in length being accompanied by a display of force. As the fibrUs shorten, they tend to bring the motionless bones closer together, and to impart motion, wliich may be rapid, and more or less forcible. If one bone is stationary, the other may be brought towards it V)y the muscular contraction, or if both are not fixed, both may move. The nervous force produces the muscular contraction, whose vigoiu- and lasting power depend a great deal upon the supply of blood sent to the fibrils through the blood vessels (arteries), and removed through the In the principal act of climbing hand-over-hand, a bough or some stationary object is grasped by the fingers, the arm being straight, and the body hanging, as it were, to it. The fii-st motion is the lifting up of the arm ; the second is the grasping with the hand; and the third is the bending of the straight elbow, and bringing the shoulder up nearer the fijced j)oint, or the part grasjicd. Whilst. this is being done the body is not limp, but more or less stiflened by the spine, which runs down the back, and consists of many bones, being made rigid by the contraction of many small muscles. Now the bones and muscles of all the parts of the body engaged in climbing are so arranged that the spine shall not suffer any jarring, but shall be lifted up safely. Were all the muscles which pull upon the arms attached to it, every unusual efibrt would drag it almost
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