-If. INFRASPINATUS. 257 



"border of the acromion, and the contiguous border of the metacro- 

 mion to near the tip of the latter. 



Insertion. — ^Most of the fibers seem to terminate upon the ectal 

 surface of the tendon of the spino-deltoideus, but the ectal layers, 

 especially at the borders of the muscle, are connected with the bone 

 by a thin, tendinous sheet, which is attached along a shorter and 

 straighter line than that of the insertion of the muscle just named 

 and between it and the insertion of the ectal layer of the ectopecto- 

 ralis. The proximal end of the line of insertion is 3-4 mm. ventrad 

 and distad of the proximal end of the line of insertion of the spino- 

 deltoideus. 



M. INFRASPINATUS. 



§ 678. Synonymy. — The human infraspinatus, &., A, 405, Q., A, I, 300; " sous-epi- 

 neux," S.-D. , A, II, 344 ; " sous-epineux," Ch., A, 265 ; siipraspinatus, Ch. (FL), A, 351 ; 

 infraspinatus, Miv., B, 148. 



Figures. — Ectal aspect (67, 74) ; origin area (44) ; insertion area (68). 



Posture. — As for the M. supraspinatus. 



Exposure. — By the reflection of the MM. spino-trapezius, leva- 

 tor claviculce, spino-deltoideus and acromio-deltoideus. 



General Description. — From the infraspinous fossa to the 

 J^ossa trocMteriana of the humerus (Fig. 45, Bj. 



Dissection. — The rounded mesoscapular border may be seen 

 between the head of the humerus and the metacromion, where it is 

 overarched by the acromion. The border is, for the most part, in 

 close contact with the small micostalis, but close to the humerus 

 is an interval filled by connective tissue. Follow this interval 

 nearly to a point opposite the metacromion, and then divide the 

 infraspinatus. 



In reflecting the humeral part, note a synovial bursa between 

 the tendon and the dorsal slope of the fossa of insertion. The scap- 

 ular half separates readily from the micostalis (marked teres minor 

 upon the figures), but from the teres, nearer the vertebral end of the 

 scapula, it can be separated only by cutting fibers. 



Origin. — By fleshy fibers from the entire supraspinous fossa, and 

 by short, tendinous fibers from the raphe between it and the teres. 



Insertion. — By a strong tendon into the ventral half of a depression 

 {Fs. trocMteriana, § 404) upon the cephalic aspect of the trochiter. 

 The proximal end of the insertion is almost in contact with the attach- 

 ment of the supraspinatus upon the crest of the trochiter. The 

 17 



