416 MEDIAN NERVE. 



The EXTERNAL CUTANEOUS NERVE (musculo-cutaneous, perforans Cas- 

 serii) arises from the brachial plexus in common with the external head of 

 the median ; it pierces the coraco-brachialis muscle and passes between 

 the biceps and brachialis anticus, to the outer side of the bend of the el 

 bow, where it perforates the fascia, and divides into an external and in- 

 ternal branch. The branches pass behind the median cephalic vein, the 

 external, the larger of the two, taking the course of the radial vein and 

 communicating with the branches of the radial nerve on the back of the 

 hand ; the internal and smaller following the direction of the supinator 

 longus, communicating with the internal cutaneous, and at the lower third 

 of the fore-arm sending off a twig, which accompanies the radial artery to 

 the wrist, and distributes filaments to the synovial membranes of the joint. 



The external cutaneous nerve supplies the coraco-brachialis, biceps and 

 brachialis anticus in the upper arm, and the integument of the outer side 

 of the fore-arm as far as the wrist and hand. 



The INTERNAL CUTANEOUS NERVE is one of the internal and smaller of 

 the branches of the axillary plexus ; it arises from the plexus in common 

 with the ulnar and internal head of the median, and passes down the inner 

 side of the arm in company with the basilic vein, giving off several cuta- 

 neous filaments in its course. At about the middle of the upper arm it 

 pierces the deep fascia by the side of the basilic vein and divides into two 

 branches, anterior and posterior. The anterior branch, the larger of the 

 two, divides into several branches which pass in front of, and sometimes 

 behind, the median basilic vein at the bend of the elbow, and descends in 

 the course of the palmaris longus muscle to the wrist, distributing filaments 

 to the integument in their course and communicating with the anterior 

 branch of the external cutaneous on the outer side, and its own posterior 

 branch on the inner side of the fore-arm. The posterior branch sends off 

 several twigs to the integument over the inner condyle and olecranon, and 

 then descends the fore-arm in the course of the ulnar vein as far as the 

 wrist, supplying the integument on the inner side of the fore-arm and 

 communicating with the anterior branch of the same nerve in front, and 

 the dorsal branch of the ulnar nerve on the wrist. 



The LESSER INTERNAL CUTANEOUS NERVE, or nerve of W -isb?.rg, the 

 smallest of the branches of the brachial plexus, is very irregular in point 

 of origin. It is a long and slender nerve, and usually arises from the 

 common trunk of the last cervical and first dorsal nerve. Passing down- 

 wards into the axillary space it communicates with the external branch 

 of the first intercosto-humeral nerve, and descends on the inner side of 

 the internal cutaneous nerve, to the middle of the posterior aspect of the 

 upper nrm, where it pierces the fascia and is distributed to the int. ^mnent 

 of the elbow, communicating with filaments of the posterior h-anc'i of the 

 'nternal cutaneous and with the spiral cutaneous. In its course it gives 

 off two or three cutaneous filaments to the integument of the inner and 

 anterior aspect of the upper arm. 



The MEDIAN NERVE has received its name from taking a course along 

 tne middle of the fore-arm to the palm of the hand ; it is, therefore, inter- 

 mediate in position between the radial and ulnar nerves. It commences 

 by two heads, which embrace the axillary artery ; lies at first to the outer 

 side of the brachial artery, which it crosses at its middle ; and clt scends 



