704 



THE NEKVOUS SYSTEM. 



' Short subscapular 



Lower subscapular 

 Axillary nerve 



thoracic nerve alone. These nerves supply the pectoralis minor muscle, and, after 

 piercing it, supply the sternal part of the pectoralis major. The inferior nerve, in many 

 cases, sends its branches to the pectoralis major round the inferior border of the 



pectoralis minor, and on its 



Thoraco-dorsai nerve wav it may supply the axillary 



arches, if present. These two 

 branches are derived the 

 superior from the seventh and 

 eighth cervical, and first thoracic 

 nerves; the inferior from the 

 eighth cervical and first thoracic 

 nerves. The pectoral muscles are 

 thus both supplied by the two 

 anterior thoracic nerves. The 

 clavicular fibres of the pectoralis 

 major are innervated by the fifth 

 and sixth nerves; the sternal 

 fibres, from above downwards, 

 by the fifth, sixth, seventh, and 

 eighth cervical, and first thoracic 

 nerves ; and the pectoralis minor 

 is supplied by the seventh and 

 eighth cervical, and first thoracic 

 nerves. 



NERVUS MUSCULOCUTANEUS. 



The musculo - cutaneous 

 nerve takes origin from the 

 lateral cord of the plexus, from 

 the fifth and sixth cervical 

 nerves (Fig. 614). The nerve 

 to the coracobrachialis muscle, 

 arising from the seventh or 

 sixth and seventh nerves, is 

 usually associated with it. 

 Separating from the lateral 

 head of the median nerve, the 

 musculo -cutaneous nerve lies 

 at first between the coraco- 

 brachialis muscle and the 

 axillary artery. It is then 

 directed distally between the 

 two parts of the coracobrachi- 

 alis, and passes between the 

 biceps and brachialis muscles, 

 to the bend of the elbow. It 

 pierces the deep fascia over the 

 front of the elbow, between 

 the biceps and brachioradialis, 

 and terminates as the lateral 

 cutaneous nerve for the supply 

 of the lateral aspect of the 

 forearm. In its course it 

 may send a branch under the biceps to join the median nerve. 



The branches of the nerve are muscular and cutaneous. The muscular branches 

 are supplied to the two heads of the biceps and the brachialis, as the nerve lies 

 between the muscles. The nerve to the coracobrachialis (usually incorporated 

 with the trunk of the musculo-cutaneous nerve) has an independent origin from 



Musculo-cutaneous nerve 



Radial nerve 



Post. cut. nerve of upper arm 

 Nerve to coracobrachialis 



Nerve to long head of triceps 



Nerve to medial head of triceps 

 (collateral ulnar) 



Nerve to brachialis ... 



Nerve to brachialis muscle 



Nerve to brachioradialis muscle- 



Nerve to extensor carpi 

 radialis longus 



Superficial ramus of radial.... 



Deep ramus of radial~- _ 



Branch to supinator muscle___ 

 Branch to extensor carpi 

 radialis brevis 



FIG. 616. THE DEEPER NERVES OF THE ARM. 



