FOREARM AND HAND 129 



white lines. At the wrist it becomes continuous, anteriorly, 

 with the volar carpal ligament and the transverse carpal liga- 

 ment (O.T. ant. annular lig.\ whilst posteriorly it forms an 

 obliquely placed, thickened band, the dorsal carpal ligament 

 (post, annular lig.). 



VOLAR SURFACE AND MEDIAL BORDER OF THE FOREARM. 



In this dissection the following structures will be dis- 

 played : 



1. The radial and ulnar arteries and their branches. 



2. The median and ulnar nerves and their branches. 



3. The deep branch and the superficial branch of the radial nerve. 



4. The group of pronator and flexor muscles. 



Dissection. The deep fascia must now be removed from the 

 forearm. Make two incisions through it, (i) a transverse 

 incision at the proximal border of the transverse carpal liga- 

 ment ; (2) a longitudinal incision from the apex of the cubital 

 fossa to the transverse incision. As the transverse incision is 

 made be careful not to injure the palmar cutaneous branches 

 of the median and ulnar nerves, the tendon of the palmaris 

 longus, the ulnar nerve and artery, and the mucous sheaths 

 of the flexors. The two palmar cutaneous nerves and the 

 tendon of the palmaris longus and the ulnar nerve and artery 

 pierce the deep fascia proximal to the transverse ligament and 

 pass across its superficial surface, but the ulnar nerve and artery 

 are bound down to the ligament by a more superficial band 

 called the volar carpal ligament, which passes from the pisiform 

 bone to the front of the transverse carpal ligament. The volar 

 carpal ligament is apt to be mistaken for the transverse liga- 

 ment, but the mistake should not be made, because the volar 

 carpal ligament lies superficial to the ulnar artery and nerve, 

 whilst the transverse ligament is deep to those structures. 

 Retain the volar carpal ligament in the meantime. The mucous 

 sheaths of the tendons lie immediately subjacent to the deep 

 fascia. Turn the two flaps marked out by the incisions to their 

 respective sides, dividing the septa which pass from their deep 

 surfaces between the adjacent muscles. Both flaps can be 

 followed to the dorsal border of the ulna, to the whole length of 

 which the deep fascia is attached, but for the present do not 

 reflect the lateral flap beyond the radial border of the forearm. 

 Near the elbow the muscles which spring from the medial and 

 lateral epicondyles gain additional origin from the deep surface 

 of the fascia. Where that is the case the fascia must be left 

 in situ, for attempts to remove it will only result in laceration of 

 the muscles. 



Muscles of the Volar Aspect of the Forearm. The 



muscles of the volar aspect of the forearm are arranged in a 

 superficial and a deep group. They comprise the flexors of 

 the wrist and digits, and also the pronators of the forearm. 

 VOL. i 9 



