314 THE MUSCLES. 



B. Inteenal Scapular Region. 



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

 of the arm {teres internus), and the flexor hrachii — are situated on 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 transverse direction. The fourth, 

 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 remove the s-light internal scapular fascia. Be careful to preserve the termina- 

 tion of the latissimus dorsi muscle, in order that its relations and adhesions v?ith the adductor of 

 the arm may be studied ; leave also the humeral insertion of the pectoralis magnus, 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 Fig. 181. With regard to the small scapulo-humeral muscle, it ought to 

 be dissected at the same time as the short flexor of the forearm. 



1. SUBSCAPULARIS (Fig. 181, 3). 

 Synonym. — Subscapulo-trochineus — Girard. 



Situation — Direction — Form. — This muscle, lodged in the subscapular fossa, 

 the name of which it bears, has 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, which singularly 

 increase the tenacity of the muscle ; the superficial fibres are spread over the 

 internal surface in glistening, nacrous layers. 



Attachments. — The subscapularis has its origin from the whole extent of the 

 fossa of that name. Its movable insertion takes place on the internal tuberosity 

 of the humerus, by means of a voluminous tendon it offers at its inferior ex- 

 tremity. A particular small synovial bursa facilitates the gliding of this tendon 

 over the eminence into which it is inserted. 



Relations. — Externally, with the scapula. Its internal face is applied against 

 the serratus magnus, from which it is separated by a thick layer of connective tissue, 

 as well as by the rudimentary fascia covering the three muscles of the internal 

 scapular region in common. Its anterior border, margined by the supra-spinatus, 

 adheres closely to that muscle in its upper two-thirds, and forms with it, by its 

 inferior third, the intermuscular space that lodges the subscapular vessels and 

 nerves. Its posterior border responds to the adductor of the arm, with which it 

 also unites for the greater part of its extent ; it is isolated from tliis muscle, in its 

 inferior third, by the interspace lodging the subscapular vessels and nerves. Its 

 terminal tendon covers the capsule of the scapulo-humeral articulation, which it 

 powerfully binds ; it is in part covered by the tendon of origin of the coraco- 

 humerahs muscle, which glides over its surface as on a pulley, by means of a 

 synovial bursa. 



Action. — This muscle is principally, and perhaps exclusively, an adductor of 

 the arm. It may be admitted, however, that it rotates the humerus inwards. 



