ANTERIOR THORACIC NERVES 1043 



of the Flexor carpi ulnaris. There is loss or impairment of sensation on the palmar surface 

 of the thumb, index, middle, and outer half of the ring fingers, and on the dorsal surface of the 

 same fingers over the last two phalanges; except in the thumb, where the loss of sensation is 

 limited to the back of the last phalanx. In order to expose the median nerve for the purpose 

 of stretching it an incision should be made abng the radial side of the tendon of the Palmaris 

 longus muscle, which serves as a guide to the nerve. 



The ulnar nerve is liable to be injured in wounds of the forearm. When paralyzed, there 

 is loss of power of flexion in the ring and little fingers; there is impaired power of ulnar flexion 

 and adduction of the hand; there is inability to spread out the fingers from paralysis of the 

 Interossei; and there is inability to adduct the thumb. The fingers cannot be flexed at the first 

 joints, and cannot be extended at the other joints. A claw hand develops, the first phalanges 

 being overextended and the others flexed. Sensation is lost or impaired in the skin of the ulnar 

 side of the hand anteriorly and posteriorly, involving the little finger, the ring finger, and the 

 ulnar half of the middle finger posteriorly, and anteriorly involving the little finger and the ulnar 

 half of the ring finger. In order to expose the nerve in the lower part of the forearm, an 

 incision should be made along the outer border of the tendon of the Flexor carpi ulnaris, and 

 the nerve will be found lying on the ulnar side of the ulnar artery. 



The miuculospiral nerve is probably more frequently injured than any other nerve of the 

 upper extremity. In consequence of its close relationship to the humerus as it lies in the mus- 

 cuiospiral groove, it is frequently torn or injured in fractures of this bone, or subsequently 

 involved in the callus that may be thrown out around a fracture, and thus pressed upon and its 

 functions interfered with. It is also liable to be squeezed against the bone by kicks or blows ; 

 it may be divided by wounds of the arm. When paralyzed, the hand is flexed at the wrist and 

 lies flaccid. This condition is known as drop wrist. The fingers are also flexed, and on an 

 attempt being made to extend them the last two phalanges only will be extended through the 

 action of the Interossei, the first phalanges remaining flexed. There is no power of extending the 

 wrist. Supination is completely lost when the forearm is extended on the arm, but is possible to 

 a certain extent if the forearm is flexed so as to allow of the action of the Biceps. The power 

 of extension of the forearm is lost on account of paralysis of the Triceps. Loss of sensation 

 may be considerable or slight. Its area is shown in Fig. 763. The best position in which to 

 expose the nerve for the purpose of stretching is to make an incision along the inner border of 

 the Brachioradialis muscle, just above the level of the elbow-joint. The skin and superficial 

 structures are to be divided and the deep fascia exposed. The white line in this structure indi- 

 cating the border of the muscle is to be defined, and the deep fascia divided in this line. By now 

 raising the Brachioradialis the nerve will be found lying beneath it, on the Brachialis anticus 

 muscle. 



Postanestketio paralysis. When a person emerges from the influence of a general anesthetic 

 palsy of the arm may be found to exist. The brachial plexus may have been compressed during 

 the operation by drawing the arm strongly from the body or elevating it by the side of the head. 

 In such a case the plexus was compressed by the head of the humerus (Braun). 



The median nerve is stretched when the arm is rotated externally and drawn backward and 

 outward. The ulnar nerve is stretched when the forearm is flexed and supinated (Braun). 

 Garrigues believes that in most cases of postanesthetic paralysis the brachial plexus was squeezed 

 between the collar bone and the first rib by the head of the patient being drawn to the opposite 

 side or being allowed to fall back. 



The Anterior or Ventral Divisions of the Thoracic Nerves (rami anteriores). 

 The anterior primary divisions of the thoracic nerves are twelve in number on 

 each side. Eleven of them are situated between the ribs, and are therefore 

 termed intercostal; the twelfth lies below the last rib. Each nerve is connected 

 with the adjoining ganglion of the sympathetic by one or two filaments (ramus 

 communicans). The intercostal nerves are distributed chiefly to the parietes 

 of the thorax and abdomen and differ from the anterior divisions of the other 

 spinal nerves in that there is no plexus formation, each nerve running an inde- 

 pendent course. The first two nerves supply fibres to the upper limb in addition 

 to their thoracic branches; the next four are limited in their distribution to the 

 parietes of the thorax; the five lower supply the parietes of the thorax and abdomen; 

 the twelfth thoracic is distributed to the abdominal wall and the skin of the buttock. 



The Anterior Division of the First Thoracic Nerve divides into two branches; 

 one, the larger, leaves the thorax in front of the neck of the first rib, and enters 

 into the formation of the brachial plexus; the other and smaller branch runs along 

 the first intercostal space, forming the first intercostal nerve (11. intercostalis /), 



