An academic physiology and hygiene .. . the head or ball of the humerus. d, rim of the socket of the scapula. e, processes of bone that overlap and protect the joint. 19. Each shoulder contains two bones, the clavicle(Lat. clavis, a key), so named from its resemblance to anancient key, and commonly known as the collar-bone;and the scapula (Lat., the shoulder) or shoulder-blade,the broad, flat, triangular bone at the top and back ofthe chest. One end of each clavicle joins the top of thebreast-bone, and the opposite end joins the shoulder-blade,thus acting as a brace to prevent the shoulder fro
An academic physiology and hygiene .. . the head or ball of the humerus. d, rim of the socket of the scapula. e, processes of bone that overlap and protect the joint. 19. Each shoulder contains two bones, the clavicle(Lat. clavis, a key), so named from its resemblance to anancient key, and commonly known as the collar-bone;and the scapula (Lat., the shoulder) or shoulder-blade,the broad, flat, triangular bone at the top and back ofthe chest. One end of each clavicle joins the top of thebreast-bone, and the opposite end joins the shoulder-blade,thus acting as a brace to prevent the shoulder from inclin-ing unduly toward the chest. The scapula has no jointwith the chest, but is held in position by strong musdeswhich cross and overlap it in various directions ; it is mov-able in a variety of directions. A shallow cavity in eachscapula receives the rounded head of the bone of the arm,and with it forms the shoulder-joint. Bony projections over-. THE OSSEOUS SYSTEM. 2/ lap the joint, give it additional security, and afford attach-ment for ligaments. The shallowness of the cavity of theshoulder-joint gives it the greatest range of movement,but also renders it more liable to dislocation. 20. The arm (upper-arm) contains one long bone, thehumerus (Lat., the arm), enlarged at its extremities to pro-vide joint surfaces at the shoulder and the elbow. Theshaft of this bone is surrounded by powerful muscleswhich use it as a lever. EXPLANATION. All the bones of the arm, fore-arm,and hand, are here exhibited in con-nection, with reference to impressingit on the mind, after having read ashort description of the individual partsof the upper extremity. a is the head of the arm-bone, artic-ulated to the shoulder. b, the joint, or elbow, formed by theulna and lower end of the arm. c, the shaft of the os humeri, or arm. d, the radius, or handle of the hand,united solely to the wrist. g, the ulna, which alone forms withthe arm the joint. 21. T
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