PLATE X. 



SUPERFICIAL PALMAR ARCH, ETC. 



In this dissection the palmaris brevis and the greater portion of the palmar fascia 

 have been removed, leaving only the outer edge of the fascia to show where it blends with 

 the origin of the abductor pollicis, and outer head of the flexor brevis pollicis. 



The superficial palmar arch may be completed hi three ways: (1) most commonly 

 by the inosculation of the superficial branch of the 

 ulnar with the radialis indicis of the radial ; or (2) 

 by inosculation with the superficialis volae ; occa- 

 sionally (8) by both. 



The position of the superficial arch may be 

 marked on the palm, by extending the thumb and 

 drawing a line a 6 from its web across the palm : 

 this will indicate the summit of the arch. The 

 deep palmar arch is generally about a finger's 

 breadth higher up. 



(In the outline the artist has not carried the 

 superficial arch quite low enough down.) 



(c) radial artery ; (d) ulnar artery ; (e) 

 superficialis volaa ; (/) radialis indicis. 



The diagram also shows in shaded lines the 

 common arrangement of the synovial sheaths of 

 the tendons in the palm, and it will be seen that 

 while the sheaths of the index, middle, and ring 

 fingers are shut off from the common synovial 



membrane of the flexor tendons at the wrist, about the level of the metacarpo-phalangeal 

 joint, that of the little finger is continuous with it ; the flexor tendon of the thumb 

 has, as a rule, a sheath to itself running down under the annular ligament, but in some 

 cases communicating with the other sheath at the wrist. 



Thus inflammation in the sheath of either the thumb or little finger has a clear 

 path to spread down under the annular ligament, and may do a considerable amount 

 of damage. 



