Outlines of human osteology / by F.O. Ward.

  • Frederick Oldfield Ward
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of human osteology / by F.O. Ward. Source: Wellcome Collection.

    372/392 page 352
    JUMPING. less proportion of its arc. Thus, in tlie storming-pace, the limb IS planted as soon as it has swung through half its arc, and arrived vertically under the trunk : in walking, as each step occupies more time, so the swinging leg describes more than half its arc, and passes beyond the vertical position before it is planted; and this so much the more as the pace is slower, and the duration of each step consequently longer. In the quickest running, each leg must, as in the storming-pace, perform at least half an oscillation (so as to hang verticallj Ijeneath the trunk) before it can be planted ; but the steps, in running, can nevertheless follow each other more rapidly than in the storming-pace ; because, as both legs are suspended in the an- at once, during part of each step, they swing forward simultaneously through a portion of their respective arcs, and, by this saving of time, can be planted in quicker succession than when they are swinging separately, one after the other. 429. This account of walking and running is so far calculated to elacidate, in their more important parti- culars, the fom- occasional modes of progression, that it will not be necessary to dwell on these latter at any great length. 430. In ywrn^MTCgr, the body is jirojected into the air by a simultaneous extension of both legs, performed with remarkable rapidity and force. In jumping, forward, back- ward, or to either side, the body describes in its flight a parabolic curve ; in jumping upward, it moves in a right line ; in all cases it obeys the ordinary laws of projectiles. Thus, for example, the period of its fall is nearly equal to that of its ascent; and its rate of motion, at each point of its descent, is exactly equal to its rate of motion at the corresponding point of its ascent. If the act of springing forward be preceded by a run, the body acquires an im- petus, which concurs with the j^i'opelling action of the limbs, and increases the horizontal extent of the leap. In like manner, by swinging the arms, at the moment of springing, in the direction in which the body is projected, their inertia is made to aid, instead of impeding, its flight through the air. 431. The progression of the body through the water, in sivhnming, dejjends on the principle that action and re- action are equal and contrary. The action, in swimming, consists in displacing a considerable quantity of water, and urging it backward, by certain movements of the
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