Applied anatomy and kinesiology, the mechanism of muscular movement . gether with its large angle of pull,gives the muscle great power as well as speed. The origin of themiddle head on the scapula enables that part to act on the shoulder-joint as well as the elbow; a rubber band looped around the olec-ranon and held at the point of origin shows plainly that its pullis chiefly lengthwise of the humerus, lifting its head up into theglenoid cavity. If the humerus is lifted the tension on the rubberband is increased, showing that it is able to aid in depressing thearm, but its angle of pull is her
Applied anatomy and kinesiology, the mechanism of muscular movement . gether with its large angle of pull,gives the muscle great power as well as speed. The origin of themiddle head on the scapula enables that part to act on the shoulder-joint as well as the elbow; a rubber band looped around the olec-ranon and held at the point of origin shows plainly that its pullis chiefly lengthwise of the humerus, lifting its head up into theglenoid cavity. If the humerus is lifted the tension on the rubberband is increased, showing that it is able to aid in depressing thearm, but its angle of pull is here very small. IIS MOVEMENTS OF ELBOW AND FOREARM Loss of the triceps destroys a persons ability to extend the elbowforcibly, but does not disable him for light tasks, since the weightof the forearm will extend the elbow when there is no resistance,making it possible to use the hands in any position when the move-ment requires little force. Stimulation of the different parts of the triceps causes extensionof the elbow with great speed and power. Duchenne states that. Fig. 66.—The triceps in action. 0, outer portion; M, middle portion; /, inner portion. the long head has much less power to extend the elbow than theother two parts, but this is no doubt due largely to the fact that heused electric stimulus when the subject was standing at ease, thescapula and humerus not being held in plaqe firmly as they are innormal coordinated action. The action of the long head to depressthe humerus and lift the humerus lengthwise is plainly shown inDuchennes experiments. The triceps can be seen and felt in vigorous action in all move- BICEPS 119 ments involving forcible extension of the elbow; its action is promi-nent in such exercises as boxing, putting the shot, driving nails,thrusting dumb-bells, pushing a lawn mower, chopping with anax, shovelling, etc. BICEPS. A prominent muscle on the front side of the upper arm with twoseparate places of origin (Fig. 50). Origin.—(1) The outer or lo
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