758 



SPINAL NERVES. 



the inner part of the coronoid process of the 

 ulna, and then takes a vertical course down 

 the fore arm, covered over by the flexor carpi 

 ulnaris, and between it and the flexor digi- 

 torum profundus. It gradually inclines to the 

 surface, and at the lower third of the fore- 

 arm becomes sub-aponeurctic, and passes 

 from between the flexor carpi ulnaris and 

 inner tendon of the flexor sublimis to the 

 lower part of the anterior surface of the 

 annular ligament, passing along it in a distinct 

 sheath with the artery, in close contact with, 

 and external to, the pisiform and unciform 

 bones, and divides into its terminal branches. 

 In the upper part of the arm the ulnar nerve 

 is in relation with the axillary artery, which is 

 placed between it and the median, nearer 

 however the latter. In the upper part of the 

 fore-arm it is about half an inch or more dis- 

 tant from the artery, but gradually inclines, so 

 as to come in close relation with, but internal 

 to it, in the two lower thirds of the fore-arm, 

 and in the pnlm of the hand. 



The ulnar gives off' no branches in the arm ; 

 and the first that comes off' from it, is when 

 the nerve is placed between the two heads of 

 the flexor carpi ulnaris. There are several 

 small articular filaments which enter the inner 

 part of the joint, and three or four which are 

 distributed to the above muscle. In the 

 upper third of the fore-arm some filaments are 

 again given off to the flexor carpi ulnaris, and 

 others for the supply of the inner half of the 

 flexor digitorum profundus. About the mid- 

 dle a small branch is given off, which, after 

 sending satellite filaments to accompany the 

 ulnar artery, perforates the fascia, and be- 

 comes cutaneous to communicate with the 

 internal cutaneous. The largest branch, how- 

 ever, given off from the ulnar, comes away 

 about two inches above the wrist-joint, and is 

 named, its dorsal branch (dorsalis carpi ulna- 

 ris : internal dorsal nerve). This winds down- 

 wards and inwards, and having passed be- 

 tween the tendon of the flexor carpi ulnaris 

 and the bone, perforates the fascia at the back 

 of the fore-arm, and becomes cutaneous a 

 little above the styloid process. It runs then 

 along the inner edge of the carpus ; and on 

 the posterior annular ligament terminates in 

 two branches. The inner branch passes along 

 the inner and back part of the metacarpal 

 bone, and phalanges of the little finger, supply- 

 ing the integument as far as its extremity, and 

 sending in its course some small filaments to 

 the abductor minimi cligiti. The outer branch 

 crosses obliquely the tendon of the extensor 

 minimi digiti, and on the fourth interosseous 

 space sub-divides. The inner sub-division 

 at the extremity of the space bifurcates in 

 order to supply the opposed sides of the little 

 and ring finger. The outer sub-division at 

 the lower extremity of the third interosseous 

 space having communicated with the dorsal 

 branch of the radial, similarly bifurcates for 

 the supply of the integument of the opposed 

 sides of the middle and ring finger. The 

 dorsalis carpi ulnaris, independently of the 

 above branches, sends numerous filaments to 



the inner and back part of the wrist and hand, 

 and communicates above with the external or 

 posterior cutaneous. 



The terminal branches of the ulnar nerve are 

 two in number, a superficial external, and deep 

 internal. The former, after a very short course, 

 divides into two branches, a small internal, and 

 large external. The internal branch passes 

 along the ulnar side of the little finger to its 

 extremity, giving filaments in its course to the 

 muscles of the little finger. The external 

 passes obliquely across the flexor tendons 

 for the ring finger, gives a filament to the 

 fourth lumbricus, and one of communication 

 with the median, and over the fourth inter- 

 osseous space at a variable distance from its 

 inferior extremity bifurcates : the divisions of 

 the bifurcation being distributed in a similar 

 manner with the median to the opposed sur- 

 face of the ring and little finger. 



The deep branch is directed backwards 

 and outwards between the abductor minimi 

 digiti, and the flexor brevis to the posterior 

 aspect of the adductor minimi digiti, having 

 first given off on the palm a small branch 

 which sends filaments to these three muscles. 

 It passes downwards in a curved manner, the 

 convexity of the curve looking downwards 

 and inwards, and after a short course passes at 

 an acute angle behind the deep palmar arch of 

 arteries. No branches come off from its con- 

 cavity. From its convexity and back part 

 and outer termination are derived filaments 

 which supply the two inner lumbricales, the 

 palmar and dorsal interossei, the adductor 

 and flexor brevis pollicis. The deep or per- 

 forating interosseous branches can be traced 

 through the two layers of interossei to the 

 skin on the back of the hand, where they com- 

 municate with the dorsal cutaneous from the 

 radial and ulnar nerves. 



The musculo-spiral nerve (radial} ' slightly 

 larger than the median, arises from the inner 

 and back part of the plexus, and is formed 

 particularly by the three inferior cervical and 

 first dorsal nerves. The trunk from which it 

 arises also gives origin to the circumflex nerve. 

 It passes at first from before backwards, running 

 behind the ulnar, and in front and below the 

 circumflex nerve, and having crossed the con- 

 joined tendons of the teres major, and latissi- 

 mus dorsi, inclines downwards, backwards and 

 outwards to the posterior surface of the hu- 

 merus, between it and the long head of the 

 triceps. It continues gradually inclining more 

 outwards, till it reaches the lower third of the 

 arm where it gains the outer aspect of the 

 bone, and here it passes forwards in company 

 with the superior profunda artery, to the an- 

 terior and outer aspect of the arm lying in- 

 ternal to the outer head of the triceps which 

 it perforates. It is now directed between 

 the supinator longus and brachialis anticus, 

 and then between the latter and extensor 

 carpi radialis longior, and, having reached 

 the outer and anterior part of the elbow- 

 joint, divides into an anterior and posterior 

 terminal branch. 



The branches given off from the musculo- 



