OF THE WRIST AND BACK OF HAND. 159 



into six compartments, each lined with a separate sy no- 

 vial membrane. 



Anterior Region of Wrist. The first layer of struc- 

 tures beneath the integument and aponeurosis of the 

 wrist, and described from the radial towards the ulnar 

 side, consists of the supinator longus, the radial ves- 

 sels, the flexor carpi radialis and palmaris longus, the 

 former of which perforates the denser portion of the an- 

 nular ligament, the ulnar vessels and nerve, and the 

 flexor carpi ulnaris. All these tendons have separate 

 sheaths, derived from the annular ligament and synovial 

 membranes. The second layer consists of the flexor 

 sublimis, enveloped in synovial membrane, and .the 

 median nerve, with its accompanying artery. The third 

 consists of the flexor longus pollicis and the flexor pro- 

 fundus digitorum, having their synovial sheaths in 

 common with the superficial flexor, while close on the 

 bone are the carpal branches of the radial and ulnar. 



The Posterior Region. Between the skin of the back 

 of the hand and the subcutaneous tissue are a number of 

 superficial veins and cutaneous nerves, derived from the 

 radial and dorsal branch of the ulnar. Beneath them is 

 a strong fibrous membrane, apparently continuous with 

 the dorsal portion of the annular ligament. There is a 

 deeper layer, covering the bones and interossei, which is 

 blended with the palmar aponeurosis laterally, and the 

 dorsal tendons pass between these layers. Beneath the 

 annular ligament are the six compartments for the fol- 

 lowing tendons, beginning on the radial side : (1) exten- 

 sores ossis metacarpi and primi internodii pollicis ; (2) 

 extensores carpi radialis, longior, and brevior ; (3) ex- 

 tensor secundi internodii pollicis, crossing the two former 

 very obliquely; (4) extensores digitorum, and indicis ; 



