. Applied anatomy and kinesiology. ce a little larger than the hand just below the axilla or arm-pit, its five lower sections showing plainly through the skin whenthe arm is raised against resistance, as in Fig. 39. Origin.—The outer surfaces of the upper nine ribs at the side ofthe chest. Insertion.—^The vertebral border of the scapula, from the spineto the lower angle. Structure.—In two separate parts, the upper and lower. Theupper part includes the fibers arising from the three upper ribsand diverging slightly to be inserted along the whole length of thescapula below the spine; the lower pa
. Applied anatomy and kinesiology. ce a little larger than the hand just below the axilla or arm-pit, its five lower sections showing plainly through the skin whenthe arm is raised against resistance, as in Fig. 39. Origin.—The outer surfaces of the upper nine ribs at the side ofthe chest. Insertion.—^The vertebral border of the scapula, from the spineto the lower angle. Structure.—In two separate parts, the upper and lower. Theupper part includes the fibers arising from the three upper ribsand diverging slightly to be inserted along the whole length of thescapula below the spine; the lower part is fan-shaped, the fibersarising from the lower six attachments on the ribs converging to 72 MOVEMENTS OF THE SHOULDER GIRDLE be inserted together at the inferior angle. The lower part is thickerand stronger than the upper. Action.—The fibers of the serratus extend too nearly lengthwiseof the ribs to exert much pull to move them unless the scapula israised. Its upper fibers are well situated for drawing the scapula for-. FiG. 37.—Serratus magnus, subscapularis, and teres major. (Gerrish.) ward as a whole, with rotation somewhat up or down according asto which fibers shorten most. As this motion takes place through the5 or 6 inches of its extent the swing of the clavicle on the sternumwill evidently cause the acromion to move outward slightly andthen inward, the two shoulders approaching each other rapidly asthe clavicles come forward to the farthest possible point. The SERRATUS MAGNUS 73 lower part of the muscle is in a position to produce vigorous rota-tion upward by drawing the inferior angle of the scapula how well these lower fibers are placed to associate with thetrapezius in turning the glenoid fossa upward. Stimulation of the serratus magnus verifies these conclusions,and study of defective cases also supports them. Loss of the ser-ratus has little effect on habitual posture of the scapula, but itinterferes seriouslv with forward movements of
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