Wrist and Hand. 95 



passage from the front of the wrist to the cleft between 

 the first and second metacarpal bones. 



The synovial membranes for the wrist joint and car- 

 pus are five in number, viz., one beneath the head of the 

 ulna, between it and the radius externally, and the interar- 

 ticular fibro-cartilage, below ; a second, between the lower 

 end of the radius and the under surface of the interarticu- 

 lar fibro-cartilage on the one hand, and the upper surface 

 of the first row of carpal bones on the other ; a third, be- 

 tween the contiguous margins of the two rows of carpal 

 bones and extending downwards between the lower row 

 and the heads of the metacarpal bones ; a fourth, between 

 the base of the metacarpal bone .of the thumb and the 

 trapezium ; and, lastly, a fifth between the pisiform and the 

 cuneiform bones. 



Superficial Landmarks. There are two creases 

 in front of the wrist, the lower one of which is the land- 

 mark for the upper border of the anterior annular liga- 

 ment, and for the lower border of the posterior annular 

 ligament. On the hand the lowest crease crosses the 

 necks of the metacarpal bones, and, therefore, represents 

 the upper limit of the synovial sheaths around the flexor 

 tendons of the index, middle and ring fingers, and, since 

 the lower limit of the synovial sac for the tendons under 

 the annular ligament, is the middle of the metacarpal bones, 

 there is, therefore, a space of about half an inch between 

 the synovial sheaths for the fingers and that of the palm. 

 This lowest crease represents also the point where the 

 palmar fascia breaks up into processes for the fingers, and, 

 about midway between this crease and the webs of the fin- 

 gers, are situated the metacarpo-phalangeal joints. Where 

 the second crease, i.e., the one above the lowest, crosses 

 the line of the metacarpal bone of the middle finger, re- 

 presents the limit of the convexity of the superficial pal- 

 mar arch. 



