The sides of Man’s chest, moreover, are not flat, as in the Rhinoceros and Horse, but rounded, so that the blade-bones can revolve upon them to and fro, as well as slide upwards and downwards; and the long arms—comparatively long, that is, from the shoulder to the elbow—hang quite free of the chest and form sharp angles with the blade-bones.
The blade-bones are accommodated to the shape of the chest; for, instead of being elongated in a direction parallel with the ribs, they are prolonged downwards, along the sides of the chest, at right angles with the ribs. This prolongation of the lower part of the blade-bone is very important, inasmuch as it enables the muscles to hold the bone steady upon the wall of the chest, and so gives greater power to those muscles which pass from the blade-bone to the arm and act upon the shoulder-joint. Were it not for this provision the contraction of the muscles intended to raise the arm would quite fail to produce the desired effect, and instead of it would simply cause the shoulder-blade to revolve upon a transverse axis. That is to say, when we endeavoured to raise the arm our effort would merely have the effect of raising the hinder part of the shoulder-blade.
In each of these particulars—in the form of the chest, and in the shape and direction of the shoulder-blade—the Monkey is intermediate between Man and the inferior animals. The Monkey’s chest is broad and round, in proportion to its length, if we compare it with other animals; but this is less marked than in the human chest. And you perceive that the Monkey’s back-bones project, as they do in other animals, beyond the level of the ribs. The blade-bones are also like those of Man in being prolonged downwards, and in being carried, to a certain extent, across the ribs; but their lower angles do not run so far in this direction as they do in the human skeleton.
Fig. [59]. Monkey.
The movement of raising the arm, as in carrying the hand outwards, or pointing upwards, or putting the hand upon the head, is rather a difficult one, and requires the combined action of many muscles. It is, therefore, to be avoided by persons to whom muscular straining is likely to be injurious; and the power of effecting this movement is easily impaired by accident or disease. A long time often elapses even after a slight bruise of the shoulder, before the person recovers the power of putting the hand upon the head.
The exercise of raising the arms above the head is a good one for those in health, and is much, and wisely, recommended by the directors of gymnastics. It brings many muscles into play, not only those of the shoulder, but the muscles all round about the chest, viz. those which pass from the spine and ribs, as well as from the breast-bone, head, and pelvis, to the shoulder-blade and arm; and, thus, it tends to strengthen the spine and the chest, as well as the shoulders and arms. There is, perhaps, no exercise so good as this; and it is much to be regretted that the dress of young ladies, with its paraphernalia of stays and shoulder-straps, interferes so greatly with it. The frequency among them of “pigeon-breast” and “crooked spine” must, partly, be attributed to the confinement of the arms, caused by the mode of dress and the customs of life. One of the few opportunities afforded to the arms of availing themselves of this exercise is in the dressing-room during the process of brushing the hair. I would by all means, therefore, recommend young ladies to give sufficient time and attention to this part of the toilette, and not to delegate it to the lady’s maid. If, in addition, I suggest that it be commonly done with open window, I feel sure that I shall have a deservedly great authority among them—Miss Nightingale—on my side.
Fig. [60].
Elbow-joint.
The movement at the Elbow is, merely, that of bending and straightening, in a hinge-like manner; yet there is a slight obliquity in the direction in which it takes place, an obliquity resembling that in the movement at the knee (page [39]).