154 THE SUPERIOR EXTREMITY 



which goes to the thumb, taking care to avoid injury to the 

 digital nerves of the thumb. Next separate the apex of the 

 intermediate part of the palmar aponeurosis from the tendon of 

 the palmaris longus and from the transverse carpal ligament, 

 and reflect the intermediate part of the aponeurosis distally to 

 the roots of the ringers. Do not fail to note that, from its medial 

 and lateral margins, septa pass dorsally into the palm separat- 

 ing the muscles of the thenar and hypothenar eminences from 

 the tendons of the long flexors of the fingers. The septa must 

 be divided as the aponeurosis is reflected. Continue the reflection 

 until the deep surfaces of the processes which pass to the fingers 

 are fully exposed. Note that, at the roots of the fingers, each 

 process divides into two slips. As the two slips pass dorsally 

 they form an arch over the two flexor tendons which pass into 

 the tendon sheath of the finger, and they become attached to 

 the sheath of the tendons, to the transverse ligament which binds 

 the heads of the metacarpal bones together, and to the deep 

 fascia of the dorsum of the finger. Define the distal border of 

 the transverse carpal ligament, but leave in position the part 

 of the volar carpal ligament which binds the ulnar artery and 

 nerve to the volar aspect of the transverse carpal ligament. 



The structures exposed by the reflection of the inter- 

 mediate part of the palmar aponeurosis are the contents of 

 the intermediate compartment of the palm. They are : 



1. The continuation of the ulnar artery as the superficial 



volar arch. 



2. The digital branches from the arch to the clefts between 



the fingers and to the medial side of the little finger. 



3. The terminal branches of the median nerve. 



4. The branch of the superficial division of the ulnar nerve 



to the adjacent sides of the ring and little fingers. 



5. The flexor tendons, surrounded by their mucous sheath. 



6. The proximal parts of the mucous sheaths of the index, 



middle, and ring fingers. 



7. The four lumbrical muscles. 



Fascial Compartments of the Palm. The two septa which 

 pass from the margins of the intermediate part of the palmar 

 aponeurosis into the depths of the palm have been noted 

 as they were divided. They join a layer of fascia which 

 lies on the volar surfaces of the interosseous muscles and 

 the adductor of the thumb and the deep volar arterial 

 arch. There are, therefore, in the palm, three fascial 

 compartments, which lie deep to the palmar aponeurosis. 

 (i) An intermediate compartment which contains the flexor 

 tendons, the lumbrical muscles, the superficial volar arch 

 and its branches, and the terminal branches of the median 



