Musculo-spiral Nerve 2 5 1 



clavius, the branch to the last-named muscle descending in front of 

 the third part of the subclavian artery. The fifth also gives a root to 

 the phrenic, which thus . comes from the fifth as well as from the third 

 and fourth cervical nerves. 



The nerve of Bell arises from the fifth and sixth nerves in the sub- 

 stance of the scalenus medius, and enters the apex of the axilla lying 

 on the side of the chest. Coming out through the scalenus medius, it 

 lies behind the trunks of the plexus, and posterior also to the first part 

 of the axillary artery. It supplies the serratus magnus. 



The supra-scapular nerve comes from the fifth and sixth after 

 their junction, and descends beneath the trapezius, and through the 

 supra-scapular notch, to supply the supra- and infra-spinatus, and the 

 shoulder-joint. 



Below the clavicle the nerves given off are : the external and 

 internal anterior thoracic from the outer and inner cords, respectively, 

 to the pectoralis major and minor. 



Three subscapular branches come from the posterior cord (which 

 is composed of fibres which are derived from the fifth, sixth, seventh, 

 and eighth cervical nerves, and from the first dorsal nerve) ; of these 

 three, the short subscapular supplies the subscapularis, the middle the 

 subscapularis and the teres major, and the long the latissimus dorsi. 



The circumflex, from the posterior cord (formed as above), winds 

 with the posterior circumflex artery round the surgical neck of the 

 humerus, through the quadrilateral space (p. 244), to supply the 

 shoulder-joint and the deltoid. It gives off also a gangliform twig to 

 the teres minor, and many branches to the skin over the lower part of 

 the deltoid and the upper and back part of the arm. 



The musculo -spiral, containing twigs of the fifth, sixth, seventh, 

 eighth, and first, continues the posterior cord from behind the third 

 part of the axillary artery, and winds in the spiral groove, with the 

 superior profunda artery, between the inner and outer heads of the 

 triceps, under cover of the long head. Piercing the external septum, 

 it lies between the supinator longus and the extensor carpi radialis 

 longior, on the outer side, and the brachialis anticus on the inner. In 

 front of the external condyle it divides into the radial and posterior 

 interosseous. 



It gives off an inner cutaneous branch which descends to the 

 interval between the inner condyle and olecranon, and two outer 

 cutaneous branches which are distributed along the front and back of 

 the fore-arm, almost to the ball of the thumb. 



It also sends branches to the triceps and anconeus, the supinator 

 longus and the extensor carpi radialis longior, and sometimes to the 

 brachialis anticus. 



The radial nerve descends from the musculo-spiral along the 

 inner side of the supinator longus, and at about a third of the way 

 down the fore-arm joins company with the radial artery ; near the 



