3 2o APPLIED ANATOMY. 



tendon of the palmaris longus or between it and the flexor carpi radialis. The 

 incision should be made between the muscles. A layer of deep fascia will be found 

 beneath them, which must be incised. From this point the nerve can be" followed up 

 beneath the flexor sublimis or downward beneath the annular ligament. Care is to be 

 taken not to disturb the tendons of the flexor sublimis at the wrist. 



The Ulnar Nerve. The ulnar nerve passes downward in the groove on 

 the back of the medial (internal) condyle and between the condyle and olecranon 

 process. It passes between the two heads of the flexor carpi ulnaris muscle and is 

 covered by it, lying on the flexor profundus digitorum ; when half way down the 

 forearm it becomes superficial and lies under or at the edge of the flexor carpi 

 ulnaris muscle with the ulnar artery and flexor sublimis muscle to its outer or radial 

 side. The ulnar artery joins the nerve just above the middle of the forearm. Just 

 below the elbow the artery gives off the posterior ulnar recurrent branch, which 

 passes up with the nerve behind the medial condyle. From the middle of the 

 forearm to the wrist the ulnar nerve lies behind and to the ulnar side of the artery. 



Branches. It gives muscular branches in the upper third of the forearm to 

 the flexor carpi ulnaris and ulnar half of the flexor profundus digitorum muscles. 

 It gives small articular branches to both the elbow-joint and wrist-joint. 



It also gives off anterior and posterior cutaneous branches. The anterior, one 

 or two, come off about the middle of the forearm ; one supplies the anterior surface 

 of the ulnar side of the forearm, while another, called the palmar cutaneous, runs 

 down the front of the artery to be distributed to the palm. 



The dorsal or posterior cutaneous branch is given off about 5 cm. (2 in. ) above 

 the wrist and passes downward and backward beneath the tendon of the flexor carpi 

 ulnaris, across the interval between the pisiform bone and styloid process of the ulna, 

 over the tendon of the extensor carpi ulnaris, and thence to the fingers. 



Wounds. This nerve in the forearm is not infrequently wounded. It is 

 especially liable to injury in resecting the elbow-joint. From what has been said of 

 its course and branches it will be seen that in order for paralysis of any of the 

 muscles of the forearm to be produced it must be injured high up in its upper third. 

 Then the flexor carpi ulnaris and inner half of the flexor profundus digitorum will 

 be paralyzed. If injured lower down the only muscular paralysis which will ensue 

 is that of the short muscles of the hand which it supplies. 



If the nerve is divided above the middle of the forearm the anterior cutaneous 

 nerves will be involved. If divided between that point and 5 cm. above the wrist 

 the anterior cutaneous escapes but the dorsal cutaneous branch is paralyzed. Below 

 this latter point the dorsal cutaneous branch escapes and the muscular and sensory 

 disturbances produced are on the palmar surface (except the dorsal interossei muscles). 



Operations. In all operations on the nerve it should be remembered that its 

 course is a straight line from the medial condyle to the radial edge of the pisiform 

 bone. In the lower half of its course it lies along the outer (radial) edge of the 

 flexor carpi ulnaris and this tendon will serve as a guide to it. It is here covered 

 only by skin and superficial and deep fasciae, though it may be overlapped by either 

 the artery or the edge of the tendon. If it is desired to reach the nerve in its 

 upper half it can be followed either from above downward or from below upward, 

 the fibres of the flexor carpi ulnaris muscle which cover it being split to the extent 

 necessary for proper exposure. Below the middle of the forearm the ulnar artery 

 lies to its radial side. Near the elbow the posterior ulnar recurrent artery accom- 

 panies it upward, but the nerve is far removed from the ulnar artery in this part of 

 its course. 



The Volar Interosseous Nerve and the Superficial and Deep Branches 

 of the Radial (Musculospiral). In addition to the large nerve-trunks of the 

 median and ulnar the forearm contains the volar (anterior) interosseous, and the 

 deep and superficial branches of the radial (musculospiral) nerve. 



The volar (anterior) interosseous nerve leaves the median opposite to or below 

 the bicipital tubercle of the radius ; it lies on the interosseous membrane to the ulnar 

 side of the accompanying volar interosseous artery. It supplies the outer half of the 

 flexor profundus digitorum and the flexor longus pollicis muscles, between which it 

 lies, and the pronator quadratus muscle. It is rarely wounded alone. 



