OF THE HAND 



489 



brevior. (3) About the middle of the posterior surface of the radius, for the ten- 

 don of the Extensor longus pollicis. (4) To the inner side of the latter, for the 

 tendons of the Extensor communis digitorum and Extensor indicis. (5) Oppo- 

 site the interval between the radius and ulna, for the Extensor minimi digiti. 

 (6) Grooving the back of the ulna, for the tendon of the Extensor carpi ulnaris. 

 The synovial membranes lining these sheaths are usually very extensive, reaching 

 from above the annular ligament down upon the tendons for a variable distance on 

 the back of the hand. 



Digital artery 

 Digital nerves 



FIG. 367. Palmar fascia. (From a preparation in the Museum of the Royal College of Surgeons of England.) 



The deep palmar fascia (aponeurosis palmaris^) (Fig. 367) forms a common 

 sheath which invests the muscles of the hand. It consists of a central and two 

 lateral portions. 



The central portion occupies the middle of the palm, is triangular in shape, of 

 great strength and thickness, and binds down the tendons and protects the vessels 

 and nerves in this situation. It is narrow above, where it is attached to the lower 

 margin of the annular ligament, and receives the expanded tendon of the Pal- 

 maris longus muscle. Below, it is broad and expanded, and divides into four 

 slips for the four fingers. Each slip gives off superficial fibres, which are inserted 



