252 THE MUSCLES. 



Structure. The muscular fibres entering into its composition are directed, 

 like the muscle itself, forward and downward ; they are deeply mixed with 

 strong aponeurotic lamellae. Of the two branches which terminate it 

 inferiorly the external is the strongest, and is entirely constituted by a 

 powerful tendon; the internal is both muscular and aponeurotic. 



Attachments. All the fleshy fasciculi of this muscle are fixed, either 

 directly, or through the medium of the internal aponeurotic lamellae : 1, To 

 the whole extent of the subspinatus fossa ; 2, To the acromion spine and its 

 tuberosity ; 3, To the cartilage of prolongment of the scapula ; 4, To the 

 internal face of the scapular aponeurosis fixed insertion. The movable 

 insertion of the muscle takes place, on the external tuberosity, by its two 

 terminal branches, the internal passing within the convexity : and the strong 

 tendon constituting the external branch (Fig. 119, 3') gliding, by means of 

 a synovial bursa, over the surface of this convexity, and attaching itself to 

 the roughened facet which forms the crest of the external tubercle. 



Relations. This muscle is covered by the anterior portion of the long 

 abductor of the arm, and by the scapular aponeurosis. It covers the scapula, 

 its cartilage, the fixed insertion of the large extensor of the fore-arm, and the 

 short abductor, which adheres to it in the most intimate manner at its 

 superior or aponeurotic portion. Its anterior border responds to the 

 acromion spine and superspinatus ; the posterior is bordered by the long 

 abductor of the arm. Its inferior extremity protects, outwardly, the capsule 

 of the scapulo-humeral articulation, and is concealed beneath the mastoido- 

 humeralis. 



Action. The subspinatus acts on the humerus as an abductor and out- 

 ward rotator. 



B. Internal Scapular Region. 



This is composed of four muscles : three principal, the subscapularis, 

 adductor of the arm or teres major, and the coraco-brqchialis, are situated at 

 the internal face of the scapula, and are covered by a very small fibrous 

 fascia which is formed of some scattered parallel fibres that run in a trans- 

 verse direction. The last, named the small scapulo-humeralis, is a very 

 slender fasciculus deeply lodged behind the articulation of the shoulder. 



Preparation. Turn over the limb which has served for the dissection of the preceding 

 region, and take away the slight internal scapular fascia. Be careful to preserve the ter- 

 mination of the great dorsal muscle, in order that its relations and adhesions with the 

 adductor of the- arm may be studied ; leave also the humeral insertion of the sterno- 

 trochineus, so that its union with the tendon of the coraco humeralis may be noted ; in 

 a word, prepare the region as it is represented in figure 121. With regard to the small 

 scapulo-humeral muscle, which is not shown in this preparation, it ought to be dissected 

 at the same time as the short flexor of the fore-arm. 



Subscapularis. (Fig. 121, 3). 

 Synonym Subscapulo-trochineus Girard. 



Situation Direction Form. This muscle, lodged in the subscapular 

 fossa whose name it bears, aifects the same oblique direction as the scapula. 

 It is wider above than below, and divides superiorly into three portions ; 

 so that its form exactly repeats that of the excavated surface it covers. 



Structure. The muscular fibres of the subscapularis slightly converge 

 towards its inferior extremity, and all end in a very strong, wide, and short 

 tendon. They are intermixed with deep and superficial tendinous fibres, 



