15. The subscapularis ([Fig. 77], a, and [p. 161]). Near its glenoid end, its glenoid and coracoid borders are separated by triangular intervals from the adjacent muscles. Transect the muscle by a line connecting the apices of these triangles. Carry an incision from the middle of this one to the middle of the vertebral border of the scapula, and reflect the muscle on both sides of this incision,—thus determining its area of origin. Reflect the humeral end without injuring the capsule of the joint.
16. Dissect the supraspinatus ([Fig. 75], a, and [p. 159]). Cut the strong fascia free from the border of the scapula and its spine. Then transect the muscle and reflect it, being careful not to injure the capsule of the joint.
17. The spinodeltoideus ([Fig. 75], e, and [p. 156]). Find its two borders, beginning with the caudal one. In freeing the very short cranial border do not injure the acromiodeltoideus ([Fig. 75], f). Transect and reflect the spinodeltoid.
18. The acromiodeltoideus ([p. 157], and [Fig. 75], f). Transect and reflect.
19. The infraspinatus ([p. 160], and [Fig. 75], c). Locate the borders in the region of the great scapular notch. It is difficult to separate the glenoid border from the adjacent teres minor ([Fig. 80], c). The separation should be begun at the humerus. Transect the muscle at the great scapular notch and reflect. Be careful not to injure the teres minor ([Fig. 80], c).
20. The teres major ([p. 163], and [Fig. 75], d; [Fig. 77], c) should be cut near its junction with the latissimus dorsi ([Fig. 77], e).
21. The teres minor ([Fig. 80], c, and [p. 161]) need not be cut.
22. The epitrochlearis ([p. 164], and [Fig. 65], r).
23. The triceps ([p. 166]). (a) The long head of the triceps ([Fig. 77], i; [Fig. 75], g). Find first its medial border and separate it from the medial head. Note the union of its lateral surface with the dorsal border of the lateral head by strong fascia, and then cut the fascia.
(b) The lateral head ([Fig. 75], h).