HUMAN ARM.
effected by muscles, two for each movement, which, taking,:ibc deltoid muscle; d, coraco their fixed points from the humerus and ulna, pull the brachialis muscle; r, r, radius round on the latter. The elbow-joint is ginglymoid ceps; l s e, i, extensors of , of fingers hinge-like, and therefore has strop g lateral ligaments; but d it is extremely liable to dislocations, often accompanied by and radial and ulnar sides of fracture, especially in the young. The accident being the wrist, and 1, palm of the followed by severe inflammation,- the joint is very apt to stiffen, thereby seriously (see AISKYLOSIS) deteriorating from Fascia; o, biceps.
the usefulness of the limb; it is, therefore, unadvisable to keep the limb too long iu any one position after such an injury. This joint is also very, liable to disease; but as this is confined to the ends of the bones, the small portions of the latter affected can be readily cut out, and the arm be restored to usefulness and mobility in a few weeks.
The upper extremity is supplied with blood by the brachial artery, the continuation of the axillary trunk. The veins collect into large superficial trunks, which unite at the bend of the elbow, at which situation one is frequently selected for venesection, and then pass on to the axillary, on the outside by the cephalic vein, on the inner side by the basilic. a.? • t i ir • ih. ' ? M.. i , al .... a.,- ,,e• . -, ? % a kl ii The nerves pass down as large cords by the side of the artery, and diverge from it to their ultimate distributions; the musculo-spiral soon passing round at the back to appear on the outside, and become the radial and posterior interosseous nerves; the ulnar runnino. behind the internal condyle, N, for which it has obtained the term " funny
bone," from the electric-like thrill which passes- along the arm when the nerve is struck or pressed. The median, as its name implies, keeps a middle course with the artery.
In wounds of the forearm, the bleeding is often excessive, but may be at once con trolled by pressura on the brachial artery, on the inner side of the biceps.
The arm affords excellent illustrations of some of the principles of mechanics. The insertion of the muscles so near, as will be seen, to the fulcra or centers of motion, involves a loss of power in the usual sense of the word; there is, however, a corresponding gain in velocity at the end of the lever; ,and for most of the purposes to which the hand is put, agility is of far greater moment than dead strength.
ARM. In maritime language, besides the obvious application to weapons of warfare, this term is applied to each extremity of a bibb, or bracket, attached to the mast of a ship for supporting the trestle-trees. The same name is also given to a part of the anchor. See ANCLIOR.—In military language, the infantry, the cavalry, the artillery, and the engineers are each called " an A." of the service--equivaleut to branch or department.