M. ACROMIO-TRAPEZIUS. 215 



and is connected with the subjacent parts only by small nerves and 

 vessels. It thus spans the interval between the vertebral borders of 

 the scapulae, which project slightly dorsad of the intervening verte- 

 bral region. In the next two or three eighths the median raphe of 

 the tendon is joined by a low median fascia which springs from the 

 supraspinous ligaments. Sometimes, in the cephalic eighth, the 

 muscular fibers reach the meson. The line of origin extends from 

 the caudal end of the axial spine to some point between the 1st and 

 4th thoracic spines, thus filling the interval between the spino- 

 trapezius and clavo-trapezius. 



Insertion. — In three parts : (A) the cephalic fifth is attached to 

 the ectal surface of the metacromion (Pig. 44), and is usually over- 

 lapped by the dorsal border of the levator clamculce ; (B) the cau- 

 dal fourth or fifth is attached to the ectal surface of the spino- 

 irapezius, along a dorso-caudal line forming an angle of 30-45 

 degrees with the mesoscapula ; (C) the intervening portion of the 

 muscle is inserted upon the glenoid border of the mesoscapula. 



Remark. — The most notable feature of this muscle is the wide 

 tendon of origin, which with its platetrope forms a heart-shaped 

 area with its apex directed cephalad. The office of the muscle 

 seems to be mainly that of a ligament, to prevent the separation of 

 the vertebral borders of the scapulse. 



M. CLAVO-TRAPEZIUS. 



§ 615. Synonymy. — The cephalic or clavicular portion of the human trapezius, Q., A, 

 373; Q., A, 1, 187 ; clavo-cucullaire, S.-D., A, II, 333 ; part of the "portion anterieure du 

 mastoido-humeral," Ch., A, 309 ; part of the anterior or superior portion of the mastoido- 

 humeralis, Ch. (PI.), A, 197; cephalic part of the '' cephalo-humeral" Miv., B, 147, and 

 Wood, $), 101, Fig. 23, " c." It is thought by some that this muscle does not represent 

 any part of the human trapezius. 



Figures. — Ectal aspect (66) ; ental aspect of reflected ends (67) ; clavicular end (73). 



General Description. — A wide tseniate muscle, from the occiput 

 and the cephalic part of tTie dorsimeson to the clavicle and the 

 trapezio-deltoid raphe. 



Dissection. — The larger part of the cephalic border of the hiatus 

 mentioned under the dissection of the acromio-trapezius is formed 

 by the caudal border of the clavo-trapezius. Trace this border 

 dorsad, bearing in mind its close union with the cephalic border of 

 the acromio-trapezius. Then trace it ventrad, using great care iu 

 lifting it from the subjacent levator claviculce, and noting that, ven- 



