PHYSIOLOGY, AND PATHOLOGY OF THE CHIMPANZEE. 407 



It passes downwards through the neck on the scalenus anticus 

 and it enters the thorax between the subclavian artery and vein. 

 Its general relations to the aortic arcL, vagus, heart, and root of 

 the lung are the same as in Man. Close to the diaphragm it 

 divides into five branches which subdivide. Some of these supply 

 the thoracic surface of the muscle, but others pass through it to 



Text-figure 47. 



S.C.G. ^•'^• 



S-CN. 



ML 



The cervical plexus. C 1-C 5 : cervical nerves. Other letters in text. 



supply the abdominal surface. It is accompanied by an artery 

 and a vein. It gives branches to the pleura and pericardium, 

 and communicates with the phrenic sympathetic plexus, but I 

 did not trace branches of this anastomosis to the inferior vena 

 cava, hepatic, and suprarenal plexuses. No arteria comes nervi 

 phrenici was seen. 



The Brachial Plextos (text-fig. 48). 



The plexus is formed by the lower four cervical and first dorsal 

 nerves as in Man, but the arrangements difier. Before they form 

 the plexus C 5, 6, and C 7 give ofi" the three roots of the long 

 thoracic nerve (L.T.N), and a well-marked branch runs from the 

 upper root to the first digitation of the serratus magnus (Serr. 

 Mag). C 7 and 8 also give twigs to the scalenus anticus (Seal. 

 Ant.). 



C 5 unites with the anterior division of 6 after giving off : — 



1. A nerve to the levator anguli scapulse (L.A.S), the rhomboidei 

 (R.M) and the first digitation of serratus magnus (S.A.M) ; 



2. the suprascapular 7^er17e (S-S.N). As 5 joins a division of 

 C 6 there is no upper trunk as in Man. 



6 divides into anterior and posterior divisions. 



27* 



