MUSCLES AND FASCIA OF UPPER EXTREMITY 157 



muscles of the thumb and little finger. The central 

 portion is the part commonly called the palmar fascia; 

 it consists of fibers mostly prolonged from the palmaris 

 longus, some from the annular ligament, thus form- 

 ing two superficial layers with vertical fibers, between 

 which is the palmaris brevis muscle; there is a deep 

 layer of transverse fibers. Below, the fa'scia divides 

 into four processes to join the digital sheaths; offsets 

 are sent back to the deep transverse ligament at the 

 heads of the metacarpals, forming a short canal above 

 each finger for the flexors. Between the processes 

 the transverse layer of fascia covers the lumbrical 

 muscles, digital vessels, and nerves, passing over 

 to the thumb and forefinger. At the clefts of the 

 fingers a transverse band is called the superficial 

 transverse ligament, or Gerdy's fibers. The interossei 

 muscles also have a separate fascia continued below 

 into the deep transverse ligament. 



The Radial Region. The following muscles consti- 

 tute the thenar eminence (the fleshy prominence of the 

 palm corresponding to the base of the thumb) and 

 have a great variety of description. 



Abductor pollicis. Adductor pollicis, obliquus. 



Plexor brevis pollicis. Adductor trans versus 

 Opponens pollicis. pollicis. 



The Ulnar Region. The following muscles constitute 

 the hypothenar eminence. (The fleshy prominence of 

 the palm corresponding to the fleshy part over the 

 metacarpal bone of the little finger.) 



Abductor minimi digiti. Opponens minimi digiti. 



Flexor brevis minimi digiti. Palmaris brevis. 



The Middle Palmar Region. The dorsal interossei 

 are four in number, one for each space, not rising 

 above the level of the bones, and numbered from 

 without inward. Each rises from the two bones 



