46 ANATOMY OF THE WOOD RAT 



thence for some 7 mm. caudad. Passing ventrad over the 

 side of the neck and fore chest, insertion is onto the clavicle 

 laterad of the sternomastoid. 



In Teonoma this muscle seems to be more definitely 

 triangular in shape and the origin does not usually extend 

 so far caudad along the middorsal line, thus forming a 

 narrow hiatus between this and the acromiotrapezius. 



M. acromiotrapezius (figs. 6, 28) has origin along the 

 middorsal line from the clavotrapezius to the spinotrapezius 

 for a distance of about 15 mm. Anteriorly it is continuous 

 with the former but the margins quickly diverge and it 

 continues to its insertion upon the cranial border of prac- 

 tically the entire spine of the scapula, and upon the small 

 tendon extending dorsad therefrom. 



In Neotoma the origin does not quite meet that of the 

 spinotrapezius. In Teonoma the origin begins farther 

 craniad and is thus sHghtly longer. Instead of a tendon 

 extending dorsad from the spine there is a stout fascia 

 running cranio-dorsad. 



M. spinotrapezius (figs. 6, 28) has origin from the mid- 

 dorsal line, extending from the posterior part of the origin 

 of the acromiotrapezius caudad, the more caudal portion 

 being from the dorsal fascia. Total origin is about 40 

 mm. in length. Extending ventro-craniad, insertion is 

 upon the scapular spinal tendon and upon the dorsal third 

 of the spine. 



In both Neotoma and Teonoma the muscle is relatively 

 somewhat weaker. 



The trapezius muscles are innervated by the accessory 

 nerve, and it is likely that they also receive small branches 

 from the cervical plexus, although this was not demon- 

 strated. 



M. latissimus dorsi (figs. 6, 7, 13, 29) has origin for 

 about 20 mm. upon the middorsal line, beginning at a 

 point directly medio-dorsad of the spine of the scapula. 



