Warren Harmon LeAvis 



157 



The third division, the laUssimus dorsi and teres major premuscle 

 mass, passes anteriorly along the dorsal side of the brachial plexus and 

 becomes continuous with the arm premuscle sheath at the proximal 



trapezius 

 intia. hjoid 

 apular 



lev. scap. premuscle mass 

 muscle plate column 

 / neural process 



spinal gang. 



pectoral 



premuscle sheatl 



,5th nerve 



phrenic nerve 



brachial plexus 

 sympathetic 



diaphragm 

 disc 



border vein 



hand plate 



tip 4th rib 



Fig. 8. Ventral view of the arm region of embryo CLXIII. X 40 diame- 

 ters. 



portion of the humerus. The humeral end is thicker and broader, and 

 continuous also with the arm premuscle sheath about the scapula. 



The fourth division, the pectoral premuscle mass, passes ventral to 

 the brachial plexus and joins the arm premuscle sheath near the proximal 

 end of the humerus. This pectoral premuscle mass is continuous medi- 

 ally with an irregular mass of condensed tissue which extends to the 



