Applied anatomy and kinesiology, the mechanism of muscular movement . er-joint; how the rotation of the humerus permits furthermovement; how elevation can be greater at the front than at the rear. 9. By mears of an inelastic cord attached to the mounted skeletor, find the extentof contraction of each of the nine muscles and thus find the length of their muscularfibers. 10. If the deltoid pulls with a force of 400 pounds and the supraspinatus with aforce of 200 pounds, how much will they together lift at the hand when the arm ishorizontal? Find distances and angles of pull by reference to the s
Applied anatomy and kinesiology, the mechanism of muscular movement . er-joint; how the rotation of the humerus permits furthermovement; how elevation can be greater at the front than at the rear. 9. By mears of an inelastic cord attached to the mounted skeletor, find the extentof contraction of each of the nine muscles and thus find the length of their muscularfibers. 10. If the deltoid pulls with a force of 400 pounds and the supraspinatus with aforce of 200 pounds, how much will they together lift at the hand when the arm ishorizontal? Find distances and angles of pull by reference to the skeleton. CHAPTER OF ELBOW AND FOREARM. The arm has a hinge joint at the elbow and a rotary union ofradius and ulna in the forearm. The elbow is a typical hinge joint, the humerus articulatingclosely with the ulna and slightly with the radius. The movementsare flexion and extension, taking place through an angle varyingin different subjects from 120 to 150 degrees. Extension is limitedby contact of the olecranon process of the ulna against the posterior. Fig. 64.—The elbow-joint, outer side. (Gcrrish.) side of the humerus; flexion is limited by contact of the muscleson the front of the arm. Some individuals can overextend the armat the elbow while others cannot fully extend it, the differencebeing due mainly to occupation, habitual position of the joint andvariation in the laxness of ligaments. The capsule of the joint isreinforced by strong bands of connective tissue on the outer andinner sides. The radio-ulnar union is a double pivot joint, the radius rota-ting in a ligamentous ring at the elbow and the lower ends of thetwo bones describing semicircles around each other at the ulna cannot rotate at the elbow and the radius cannot rotate 116 MOVEMENTS OF ELBOW AND FOREARM at the wrist, yet by means of the peculiar manner of union betweenthe two the hand can turn through nearly 180 degrees. This,together with the 90 degrees of rotation possible in the sh
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