Median Xeri'C 255 



send twigs over the back of the second and third phalanges and to the 

 pulp of the nail. 



The digital nerves lie beneath the superficial palmar arch, but in 

 the fingers they are superficial to the digital arteries. The median also 

 supplies the abductor, opponens, and the outer head of the flexor brevis 

 pollicis, and the two outer lumbricals. 



Thus, the ring drawn over the 'ring-finger' couples together digital 

 branches of the median and ulnar upon the palmar aspect, and of the 

 radial and ulnar on the dorsal. 



In paralysis of the median nerve the front of the fore-arm is wasted, 

 the supinator longus and flexor carpi ulnaris alone being unaffected. 

 The pronators are useless, as are also the special flexors of the fingers, 

 except the inner part of the profundus, which is supplied by the 

 ulnar. The second phalanges (flexor sublimis) cannot be flexed, nor 

 the ungual phalanges of the index- and middle fingers (outer part of 

 profundusj. The abductor pollicis being paralysed, the adductor (ulnar) 

 keeps the thumb well up against the index-finger, and wasting of the 

 muscles of the ball of the thumb becomes marked. 



Flexion of the wrist has to be accomplished entirely by the ulnar 

 flexor, and by the inner part of the deep flexor of the fingers, the hand, 

 in consequence, being deflected to the ulnar side. 



I have lately had a child under treatment whose median nerve was, 

 as seen during a subsequent operation, completely severed, yet there 

 was no loss of sensation of the skin of the hand or fingers. This pro- 

 bably was due to the presence of free communications between the 

 median and the ulnar and radial nerves, an arrangement w r hich may 

 prove as valuable in an emergency as the anastomotic loops between 

 veins or arteries. However, in paralysis of the median nerve in an 

 adult, loss of sensation must be expected in the outer part of the palm 

 (except over the ball of the thumb, where the radial is distributed), 

 in the front of the three and a-half outer digits, and also over the 

 backs of the last phalanges of those digits. The impaired nutrition 

 (trophic fibres, p. 215) in these areas is apt to be associated with 

 vesicles and sores, and with imperfect growth of the nails. 



The musculo-cutaneous comes from the outer cord (fifth, sixth, 

 and seventh), and, leaving the third part of the axillary artery on its 

 inner side, passes obliquely through the coraco-brachialis to the space 

 between the biceps and brachialis, in which it descends almost to the 

 elbow. Piercing the deep fascia, it lies beneath the median cephalic 

 vein, and divides into an anterior and a posterior branch, which supply 

 the skin down to the ball of the thumb and over the back of the wrist. 

 The musculo-cutaneous nerve supplies the coraco-brachialis, biceps, 

 and brachialis anticus, the branch to the last-named muscle sending a 

 twig to the elbow-joint. 



