HO W THE GORILLA CLIMBS . 
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most unlearned in anatomy need 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 flesh 
and skin, acts through 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 fibrils shorten, they tend to bring the motionless bones 
closer together, and to impart motion, which may be rapid, and more or less forcible. If one bone is 
stationary, the other may be brought towards it by the muscular contraction, or if both are not fixed, 
both may move. The nervous force produces the muscular contraction, whose vigour 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 veins. 
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 first 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 fixed point, or the part grasped. Whilst 
BONES or THE FORE- ARM AND ARM OF THE GORILLA — SIDE VIEW. SHOULDER OR BLADE-BONE. 
this is being done the body is not limp, but more or less stiffened 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 effort would drag it almost to pieces, so there is a wide 
flat bone placed between the spine and the arm. This so-called blade-bone is jointed by a ball and 
socket joint to the arm-bone, but is only united to the spine and back part of the head by muscles. 
Muscles start from the spine to the blade-bone, from the blade-bone to the bones of the arm and fore- 
arm, and from these last to the bones of the fingers, and by their shortening or contraction, the fingers 
being stationary, the body is at last brought closer to them. 
In order to explain the first motions of climbing, it is necessary to remark that on looking at the 
skeleton of the Gorilla the shoulder-blades are seen to be of the same general shape as those of man ; 
they are much larger, however, and there are some anatomical points about them, which clearly have 
to do with the ability of the great Ape to keep its arms up for a long tune, and to pull up its heavy 
body when the hands and fore-arms are fixed and immovable by clasping. One muscle, which in our- 
selves forms the cushion on the shoulder, and reaches down the outside of the arm for a little distance, 
is called the deltoid or A-shaped muscle, and its especial duty is, when the shoulder-blade is fixed, to 
lift up the arm by its contraction. The movement is permitted because between the spots where the 
muscles are adherent to the blade-bone on the one hand, and to the outside of the arm-bone on the 
other, a distance of several inches, there is a joint like a ball and socket. The muscle is not 
