356 



APPLIED ANATOMY. 



tudinal crease which passes to the web between the index and middle fingers. Mid- 

 way between the crease and the webs of the fingers lie the joints of the middle, ring, 

 and little finger. More stress is apt to be laid on a knowledge of these creases than 

 they deserve (Fig. 369). 



The position of the metacarpophalangeal joints is best determined by feeling for 

 them on the dorsum of the hand and then taking a corresponding point on the 

 palmar surface. They are sufficiently accurately located by taking a point 2 cm. 

 (24 m - ) behind the web of the fingers. The creases for the middle phalangeal joints 

 are directly opposite the articulations. The creases for the end phalangeal joints are 

 to the proximal side of the articulations. The deep palmar arch lies about 1.5 cm. 

 (f in. ) closer to the wrist than the superficial. 



The digital arteries from the superficial palmar arch pass downward with the 

 digital nerves, superficially, in the spaces between the metacarpal bones, to the webs 

 of the fingers. About i cm. (f in. ) behind the web they sometimes receive 

 branches from the deep palmar arch, and then divide to go to each lateral palmar 

 side of the fingers. The palmar fascia divides into its four slips just below the 

 line of the superficial palmar arch, opposite the web of the thumb. 



Flo. 369. The palmar surface of the hand showing thenar and hypothenar eminences and creases 



On the dorsum of the hand the extensor tendons can be seen. Accessory slips 

 usually connect the tendon of the ring finger with that of the little finger and mid- 

 dle finger. A slip also usually passes from the tendon of the middle to that of the 

 index finger. 



The slip from the tendon of the ring to that of the little finger has been thought 

 to restrict the freedom of the movement of the ring finger, hence in musicians it some- 

 times has been divided. The operation is done by first flexing the fingers, which 

 brings the slip well forward near the knuckle, and then introducing a thin knife longi- 

 tudinally beneath it and cutting toward the skin. The procedure has not found favor 

 among musicians. 



The metacarpal bones are subcutaneous and can readily be felt their entire 

 length. The muscular prominence on the dorsum of the hand seen when the thumb 

 and forefinger are approximated is due to the abductor indicis muscle. At its upper 

 extremity the radial artery passes between its two heads to enter the palm. When 

 the thumb is extended the snuff-box becomes evident and the extensor longus pollicis 

 tendon is distinctly seen leading to the ulnar side of the posterior radial (thecal) 

 tubercle on the middle of the dorsum of the radius. The tendons on the radial side 

 of the snuff-box are the extensor brevis and extensor ossis metacarpi pollicis. 



When the fingers are flexed, the prominence of the knuckles is formed by the proxi- 

 mal bones; the distal phalanges fold under the proximal ones and the joint line is about 

 I cm. (f in. ) below the dorsal surface of the metacarpal bones (Fig. 366, page 353). 



