75G 



SPINAL NERVES. 



median basilic vein, some occasionally pass- 

 ing in front, and some behind. The exter- 

 nal filaments course down the anterior and 

 inner part of the fore-arm, following the di- 

 rection of the median vein, and communica- 

 ting with branches of the external cutaneous : 

 the internal follows the course of the ulnar 

 vein, communicating with a twig of the ulnar 

 nerve at the lower part of the fore-arm. Both 

 terminate in the integument over the annular 

 ligament. 



The internal branch) frequently perforating 

 the fascia lower down than the external, 

 passes behind and then below the median 

 basilic vein, to the inner and back part of the 

 fore-arm, and having communicated a little 

 below the elbow with the accessory internal 

 cutaneous, continues its course, and supplies 

 the integument along the inner and back part 

 of the fore-arm as far as the inner edge of the 

 hand, communicating, in its course, with the 

 innermost filaments of the external branch. 



Placed behind and internal to the internal 

 cutaneous nerve, is the cutaneous nerve of 

 Wrisberg (the accessory nerve of the internal 

 cutaneous), considerably smaller than it. It 

 arises from the united chord formed by the 

 seventh cervical and first dorsal. It descends 

 along the inner part of the axilla, and com- 

 municates with the cutaneous branch of the 

 second intercostal. Coursing down the arm 

 on a plane behind the ulnar and internal to 

 the basilic vein, it perforates the fascia about 

 the lower third, and, becoming cutaneous, di- 

 vides into anterior filaments, communicating 

 with the internal cutaneous: and posterior, 

 communicating with the internal cutaneous 

 branch of the muscu-lo-spiral. 



The external cutaneous (musculo-cuta- 

 neous : perforans casserii), larger than the 

 preceding, but smaller than all the other 

 nerves, and most external, is formed by the 

 fifth and sixth cervical. It is directed ob- 

 liquely downwards and outwards in front of 

 the tendon of the subscapularis to the inner 

 aspect of the'coraco-brachialis, perforates this 

 muscle (occasionally, however, passes behind 

 it without perforating), and then becomes 

 situated obliquely between the biceps and bra- 

 chialis anticus. At a short distance from the 

 elbow it emerges from beneath the outer 

 border of the biceps, and internal to the 

 supinator longns ; and at the bend of the 

 elbow, after passing behind the median ce- 

 phalic vein, bcomes subcutaneous. In this 

 part of its course the external cutaneous nerve 

 gives off a series of muscular branches. Of 

 the two branches to the coraco-brachialis, the 

 upper, having perforated it, terminates in the 

 short head of the biceps. 



The branches to the biceps unite separately 

 or by a common trunk, and one of them per- 

 forates the biceps, and supplies the elbow- 

 joint, being here situated to the outside of 

 the superficial flexor tendons. 



The branches for the brachialis anticus are 

 several, and penetrate the muscle by its superfi- 

 cial surface. The continuation of the external 

 cutaneous nerve in the fore-arm is represented 



by a series of internal and exttrnal cutaneous 

 branches, which pass down along either side 

 of the radial vein. The former near the wrist 

 joins with a branch from the radial nerve, and 

 gives off a filament which perforates the fascia, 

 and accompanies the radial artery to the outer 

 and back part of the wrist, where it supplies 

 small twigs to the front and back of the radio- 

 ulnar articulation. The latter gives filaments 

 to the outer and back part of the fore arm, 

 as far as the wrist. 



The median nerve. The largest of the bra- 

 chial plexus, and situated between the external 

 cutaneous and the ulnar, arises by two roots, 

 the external common to the median, and the 

 external cutaneous : the internal common to 

 the median, the internal cutaneous, and the 

 ulnar. The fifth, sixth, seventh, and eight 

 cervical and first dorsal nerves consequently 

 concur to form it. Between its two roots is 

 placed the axillary artery. It passes along the 

 inner side of the arm in company with the 

 axillary artery to the bend of the elbow, lying 

 at first to the outside of the vessels, and then 

 a little above the middle of the arm, crosses 

 to its inner side, occasionally, however, con- 

 tinuing all along to its outside. It is slightly 

 overlapped by the inner border of the biceps, 

 having the brachialis anticus to its outside : 

 the latter muscle separates it inferiorly from 

 the ulnar nerve. The upper part of the in- 

 ternal cutaneous nerve runs along its inner side. 

 It sinks into the bend of the elbow behind the 

 semilunar fascia, and in front of the brachialis 

 anticus, passes between the two heads of the 

 pronator radii teres, and is then conducted 

 along the forearm between the flexor digi- 

 torum sublimis and profundus to the annular 

 ligament, behind which it passes ; and at the 

 lower border of this becomes expanded, and di- 

 vides into a series of terminal digital branches. 



The median nerve gives off no branches 

 during its course along the arm, with the 

 exception of an occasional communicating 

 branch to the musculo-cutaneous below the 

 level of the insertion of the coraco-brachialis ; 

 and a branch which is usually found coming 

 off from the anterior part of the trunk a little 

 above the elbow. This is directed along the 

 brachialis anticus to the pronator teres, which 

 it supplies, and sends a few filaments back- 

 wards to enter the articulation. 



The branches given off in the fore-arm are 

 muscular, interosseous, and cutaneous. 



The muscular branches for the lower part of 

 the pronator teres, flexor carpi radialis, pal- 

 maris longus, and flexor sublimis, are generally 

 derived from a primary branch, which arises 

 behind the pronator teres a little below the 

 elbow-joint ; the lower part of the flexor 

 sublimis, however, receiving several smaller 

 branches from the main trunk. The branches 

 for the flexor longus pollicis and flexor digi- 

 torum profundus are given off lower down, 

 there being generally one for the former and 

 two for the latter, the outer part of which 

 only is supplied ; the inner part of the muscle 

 being supplied by the ulnar nerve. 



The anterior interosseous nerve is the most 



