. Applied anatomy and kinesiology. n the front of the humerus makes it a rotator inward,and its position to the rear of the trunk enables it to turn it fartherthan the pectoralis major. Isolated action of the latissimus produces exactly what we wouldexpect. The upper fibers adduct the scapula so accurately andstrongly that Duchenne is inclined to place it among the musclesmaintaining normal posture of the shoulder girdle, and gives evi-dence from defective cases to sup])()rt the ()])ini()u. lie shows alsothat when the lower fibers contract with the arm at the side t\\e\ 94 MOVEMENTS OF THE SHO
. Applied anatomy and kinesiology. n the front of the humerus makes it a rotator inward,and its position to the rear of the trunk enables it to turn it fartherthan the pectoralis major. Isolated action of the latissimus produces exactly what we wouldexpect. The upper fibers adduct the scapula so accurately andstrongly that Duchenne is inclined to place it among the musclesmaintaining normal posture of the shoulder girdle, and gives evi-dence from defective cases to sup])()rt the ()])ini()u. lie shows alsothat when the lower fibers contract with the arm at the side t\\e\ 94 MOVEMENTS OF THE SHOULDER-JOINT draw the head of the humerus down from the socket as far as thecapsule will permit. Loss of the latissimus results in a forward displacement of theshoulder, due to the pull of the pectoral muscles, major and noticeably weakens all downward movements of the arm. Whenboth the latissimus and pectoralis major are lost the shoulder isapt to be too high, because of the unbalanced action of the trapeziusand Fig. 51.—The latissimus in action. The subject is depressing his arms againstresistance. Notice the narrow upper end of the latissimus just below the arm andtrace its upper and lower margins as it widens out. L is near its center; D, deltoid;T, long head of the triceps. The latissimus may be observed on the living body to act vigor-ously in all strong downward movements of the arms, such as chop-ping, striking with a hammer, and in supporting the weight of thebody on the hands; the same is seen in movements more directlyto the rear, such as rowing, paddling, and exercises on chest weightswhen the subject is facing the machine. It also acts in raising thetrunk when it is inclined slightly forward up to the erect militaryposition. The use of the latissimus in this movement is apt togive an excessive hollow in the back at the waist line unless othermuscles are used to counteract it. TERES MAJOR 95 TERES MAJOR. A small round muscle lying along the axil
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