820 ANATOMICAL TSCHNOLOGT. 



General Description. — Trapezoidal in outline ; from the caudal 

 part of the cervical dorsimeson and the cephalic part of the tJio- 

 racic, to the vertebral border of the scapula. 



Exposure. — By the removal of the MM. spino- and acromio- 

 trapezius. 



Posture. — Ventricumbent, with one or two blocks lengthwise 

 under the thorax so as to permit the ventriduction of the shoulder. 

 Usually the body must be steadied by cords or chain-hooks. Lat- 

 eriduct the vertebral border of the scapula so as to render the M. 

 rhomboideus tense. 



Dissection. — The ventro-cephalic border of the muscle has been 

 exposed by the reflection of the occipito-scapularis. The caudal 

 border may be seen along a line running nearly laterad from the 

 4th or 5th thoracic spine, opposite the gleno-vertebral angle of the 

 scapula. Note that the texture of the muscle is looser than that of 

 the irapezii, and that the caudal border is thinner than the ventro- 

 cephalic, excepting the dorso-cephalic third of the latter. This 

 muscle may be safely transected by cutting ecto-entad ; in reflecting 

 it, note that the thickest part is opposite the 1st and 2d thoracic 

 spines. 



§ 621. Origin. — In two parts : (A) from the caudal two or three 

 fifths of the cervical supraspinous ligament ; in the latter case it 

 includes the caudal two thirds of the axial spine, and thus extends 

 about 1 cm. cephalad of the acromio-trapezius ; (B) from the sides 

 of the tips of the first four thoracic spines and from the interspinous 

 ligaments caudad of each of them, excepting, sometimes, the 4th. 



Insertion. — At least two forms of insertion are found. The sim- 

 pler is as follows (Fig. 44, 45) : the cephalic tliree fourths is attached 

 by short tendinous fibers along the vertebral border of the scapula, 

 passing gradually from its ental to its ectal margin. The cephalic 

 half or third of this portion is closely united with the insertion of 

 the levator anguU scapulce. The caudal fourth is attached by 

 fleshy fibers upon the gleno-vertebral angle in apposition with the 

 origin of the teres. 



The other mode of insertion presents four divisions : (A) the 

 cephalic 8 mm. is attached by fleshy fibers to the ental aspect of the 

 lev. ang. scap. close to its insertion upon the ental margin of the 

 vertebral border of the scapula, and caudo-ventrad of the insertion 

 of the occipito-scapularis ; (B) the next 6-8 mm., constituting the 

 thickest part of the muscle, is attached by fleshy fibers to the ental 



