FOREARM AND HAND 167 



examine the relations of the deep volar arch, and the deep 

 division of the ulnar nerve. 



Arcus Volaris Profundus (O.T. Deep Palmar Arch). 

 Two arteries take part in the formation of the deep volar 

 arch, the radial and the profunda branch of the ulnar. 

 The radial, which plays the chief part, enters the palm through 

 the proximal end of the first interosseous space, between the 

 two heads of the first dorsal interosseous muscle, and in the 

 present stage of dissection it is seen appearing through the 

 cleft between the oblique and transverse parts of the adductor 

 pollicis. The arterial arcade formed by its union with the 

 profunda branch of the ulnar artery lies across the metacarpal 

 bones, immediately distal to their bases^ and across the inter- 

 osseous muscles in the intervening interosseous spaces. The 

 deep arch is, therefore, about a finger's breadth proximal to 

 the superficial volar arch, but it is in a much deeper plane, 

 for it is separated from the superficial volar arch by the 

 flexor tendons of the fingers and their mucous sheath, 

 the lumbrical muscles, branches of the median nerve and the 

 flexor digiti quinti brevis. The convexity of the deep arch, 

 which is less marked than that of the superficial arch, is 

 directed towards the fingers, and in its concavity lies the 

 deep branch of the ulnar nerve. 



The branches which spring from the deep volar arch are : 

 (i) the recurrent a few small twigs which run proximally, in 

 front of the carpus, to anastomose with branches of the volar 

 carpal arch ; (2) perforating branches, which pass dorsally in the 

 proximal parts of the interosseous spaces to anastomose with 

 the dorsal metacarpal arteries ; and (3) the volar metacarpal 

 branches three in number which pass distally, volar to the 

 interosseous spaces, and unite, near the roots of the fingers, 

 with the corresponding volar digital arteries from the 

 superficial volar arch. Sometimes the volar metacarpal 

 branches are large and take the place of the corresponding 

 volar digital arteries. 



Ramus Profundus Nervi Ulnaris. The deep branch of 

 the ulnar nerve springs from the parent trunk on the 

 volar aspect of the transverse carpal ligament, and gives 

 off a branch which supplies the three short muscles of the 

 little finger. Accompanied by the deep branch of the ulnar 

 artery, it sinks into the interval between the abductor and 

 flexor digiti quinti brevis, and turns laterally across the palm, 

 i lie 



