260 SURGICAL APPLIED ANATOMY. [Chap. xv. 



disturbed over the skin supplied by the nerve 

 (Erb). 



Paralysis of the median nerve. Flexion of 

 the second phalanx is impossible in every finger, as is 

 also a like movement of the last joint of the index and 

 middle fingers. Partial flexion of the third pha- 

 langes of the two inner digits is possible, the inner 

 part of the flexor profundus being supplied by the 

 ulnar nerve. Flexion of the first phalanx with exten- 

 sion of the second and third can still be performed 

 in all the fingers by the interossei. The thumb is 

 extended and adducted, and can neither be flexed 

 nor opposed. Bending of the wrist is only possible 

 when the hand is forcibly adducted by means of the 

 flexor carpi ulnaris, which is not paralysed. Pronation 

 is lost. Sensation is disturbed over the skin supplied 

 by the nerve (Erb). 



Paralysis of the ulnar nerve. Ulnar flexion 

 and adduction of the hand are limited. Complete 

 flexion of the two inner fingers is impossible. The 

 little finger can scarcely be moved at all. The action 

 of the interossei and two inner lumbricales is lost. 

 The patient is unable to adduct the thumb, and sen 

 sibility is impaired over the cutaneous area supplied 

 by the nerve (Erb). 



It is well to note that the skin over the back of 

 the last two phalanges of the index and middle fingers 

 and of the outer part of the ring finger is supplied by 

 the median nerve, and not by the radial, as sometimes 

 described (Fig. 29). 



After complete division of any one of the three 

 great nerves of the upper limb, the loss of sensa- 

 tion in the cutaneous parts supplied by that nerve 

 is often quite slight. This is accounted for by the 

 interlacings that occur between the principal nerves of 

 the arm, so that when a given trunk is injured the 

 sensory impressions are returned by another route. 



