MEDIAN NERVE. BRANCHES. 463 



The LESSER INTERNAL CUTANEOUS NERVE or nerve of Wrisberg, 

 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 downwards 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 arm, where it pierces the fascia and is dis- 

 tributed to the integument of the elbow, communicating with filaments 

 of the posterior branch of the internal 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 the middle of the fore-arm to the palm of the hand ; it is, there- 

 fore, intermediate 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 mid- 

 dle ; and descends on its inner side to the bend of the elbow. It then 

 passes between the two heads of the pronator radii teres and flexor 

 sublimis digitorum muscles, and runs down the fore-arm, between the 

 flexor sublimis and profundus, and beneath the annular ligament, into 

 the palm of the hand. 



The Branches of the median nerve are, 



Muscular, Superficial palmar, 



Anterior interosseous, Digital. 



The Muscular branches are given off by the nerve at the bend 

 of the elbow ; they are distributed to all the muscles on the anterior 

 aspect of the fore-arm, with the exception of the flexor carpi ulnaris, 

 and to the periosteum. The branch to the pronator radii teres sends 

 off reflected branches to the elbow-joint. 



The Anterior interosseous is a large branch accompanying the an- 

 terior interosseous artery, and supplying the deep layer of muscles in 

 the fore-arm. It passes beneath the pronator quadratus muscle, and 

 pierces the interosseous membrane near the wrist. On reaching the 



passes between the two heads of the pronator radii teres, and of the flexor sub- 

 limis digitorum. 12. Its muscular branches. 13. Its anterior interosseous 

 branch. 14. The point at which the nerve passes beneath the annular ligament 

 and divides into six terminal branches. The branch which crosses the annular 

 ligament is the superficial palmar. 15. The ulnar nerve giving off several 

 muscular branches to the triceps. 16. The point at which it passes between 

 the two heads of the flexor carpi ulnaris. 17. Its dorsal branch. 18. The ter- 

 mination of the nerve, dividing into a superficial and deep palmar branch. 19. 

 The musculo- spiral nerve. 20. Muscular branches. 21. Spiral cutaneous 

 nerve. 22. The posterior interosseous nerve piercing the supinator brevis 

 muscle. 23. The radial nerve The two last nerves are the terminal branches 

 of the musculo-spiral. 24. The point at which the radial nerve pierces the 

 deep fascia. 25. The circumflex nerve. 



