M. SFINO-DELTOIDEUS. 355 



ered by a firm fascia, whicli is closely attached along the border of 

 the mesoscapula and the coracoid border of the scapnla excepting 

 where it was separated from the subscapularis. Divide these 

 attachments, cutting from the glenoid angle of the scapula toward 

 the vertebral border, then transect the muscle at its middle, and 

 reflect both parts ; the proximal part may be wholly removed. 



Origin. — By fleshy fibers from the whole supraspinous fossa, 

 and, by the ectal fascia, from the coracoid border of the scapula 

 and mesoscapula. 



Insertion. — The muscle passes over the capsule of the shoulder 

 joint with but slight adhesions thereto, and ends in a short, thick 

 tendon which is attached to the crest of the trochiter. Between the 

 trochiter and the tip of the acromion process, the body of the mus- 

 cle is closely attached to the border of the acromio-deltoideus . The 

 distal cm. of the other — ^the coracoid — border is connected vdth the 

 insertion of the cephalic division of the entopectoralis, as described 

 under that muscle (§ 658). 



M. SPINO-DELTOIDEUS. 



§ 674. Synonymy. — The spinal, or mesoscaptilar, part of the human deltoideus, G., A, 

 404, Q., A, 1, 199 ; " delto-spinal," S.-D., A, II, 338 ; part of " long aMucteur du bras," Ch., 

 A, 263 ; part of the long abductor of the arm, or scapular portion of the deltoid, Ch. (PI.), 

 A, 349 ; part of deltoid, Miv., B, 147. 



Figures. — Ectal aspect (66, 67) ; reflected (74) ; origin area (44) insertion area (68). 



Posture. — Let the arm rest upon its caudal surface on the flat 

 side of a block, with the elbow toward the dissector. The scapula 

 may be permitted, at times, to hang over the end of the block, so 

 as to render the muscle tense. 



Exposure. — Remove the skin upon the cephalic surface of the 

 brachium to the junction of its middle and distal thirds. Remove 

 the firm fascia covering the cephalic side of the shoulder. 



General Description. — Thin, apparently subtriangular, but 

 really trapezoidal ; from the mesoscapula and metacromion to the 

 deltoid ridge (Fig. 46, 68, 69), on the proximal half of the cephalic 

 surface of the humerus. 



Dissection. — The dorsal border forms a nearly direct line be- 

 tween the tuberosity of the mesoscapula and the humerus at the 

 junction of the proximal and middle thirds. Lift it at its middle, 

 where it crosses the angle formed between the muscles upon the 



