CERVICAL NERVES. 



165 



the anterior mediastinum, frequently adhering to the pericardium, it 

 is distributed to the diaphragm by several branches. 



The four inferior cervical nerves, together with the first dorsal, 

 emerging from the spinal canal between the scalenus anticus and 

 medius muscles, form a large plexus, which is plaited around the sub- 

 clavian and axillary arteries. 



The brachial plexus gives off a scapular branch, which ascends 

 upon the shoulder and sup- 

 plies its muscles ; passing Fig. 143. 

 through the coracoid notch. 

 The thoracic branches are 

 distributed to the muscles 

 covering the parietes of the 

 thorax, with the sub-scapu- 

 lar branches, which supply 

 the muscles under the shoul- 

 der. The circumflex or ax- 

 illary nerve winds round the 

 head of the humerus, in com- 

 pany with the posterior cir- 

 cumflex artery, and is dis- 

 tributed to the deltoid muscle. 

 The i?iternat cutaneous is a 

 very small, thin filament, 

 passing down the inside of 

 the arm, and sends branches 

 across the superficial veins 

 of the elbow, then is distri- 

 buted to the skin, fascia, and 

 fore-arm. The external or 

 musculO'CutaneouS^ perfo- 

 rates the coraco-brachialis, 

 and is also distributed to the 

 muscles and integuments of 

 the fore-arm. 



The ulnar^ descending 

 the arm, it passes superficially under the internal condyle, and is 

 finally distributed to the little finger, and the ulnar side of the ring 

 finger. The radial or musculo- spiral winds around the humerus, 

 between the heads of the triceps muscles, which it supplier with 

 branches, and then descends the fore-arm supplying its muscles, a 

 large branch accompanying the radial artery, supplying the wrist and 

 thumb. 



The 7nedian'^ is the largest of these nerves which come from the 

 brachial plexus ; it descends the arm in close company with the 

 brachial artery, until it reaches the elbow ; it there passes between 



