Chap, xv.j NERVES OF UPPER LIMB. 285 



can be extended. The latter are bent and cover the 

 thumb, which is also flexed and adducted. When 

 attempts are made to extend the fingers, the interossei 

 and lumbricales alone act, producing extension of the 

 last two phalanges and flexion cf the first. Supi- 

 nation is lost, especially if the elbow be extended so 

 as to exclude the action of the biceps muscle. Ex- 

 tension at the elbow is lost, and sensibility is dis- 

 turbed 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 

 nlnar 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). 



After complete division of any one of the three 

 great nerves of the upper limb, the loss of sensation 

 in the cutaneous parts supplied by that nerve is often 

 quite slight. This is accounted for by the interfacings 

 that occur between the principal nerves of the arm, so 



