REGION OF THE WRIST. 



337 



styloid process of the ulna, the internal lateral ligament, the pisiform, and adjacent 

 carpal bones. Beneath this posterior annular ligament are six compartments. From 

 the radial toward the ulnar side they are : ( i ) One on the outer side of the styloid 

 process of the radius for the extensor ossis metacarpi pollicis and extensor brevis 

 pollicis; (2) for the extensor carpi radialis longior and brevior, then comes the 

 posterior radial tubercle in the middle of the radius, and passing close along its ulnar 

 side is (3) the extensor longus pollicis. To the ulnar side of this tendon is a com- 

 paratively broad sheath for (4) the extensor communis digitorum and the extensor 



Extensor ossis metacarpi pollicis 

 and extensor brevis pollic: 



Extensor carpi radialis 1 

 and extensor carpi radialis bre 



Extensor longus 



Extensor carpi ulnaris 



Extensor minimi digiti 



Extensor communis digitorum 

 and extensor indicis 



FIG. 347- The sheaths of the extensor tendons on the back of the wrist distended with wax to show their extent. 



indicis muscles. In the interval between the radius and ulna lies (5) the tendon of 

 the extensor minimi digiti, and on the posterior side of the styloid process of the ulna 

 is (6) the tendon of the extensor carpi ulnaris (Fig. 347). 



Each of these six compartments is lined with a separate sheath which extends 

 under the annular ligament from a centimetre or two above the joint to about the 

 bases of the metacarpal bones on the dorsal surface of the hand. 



The Anatomical Snuff-Box (la tabatiere anatomique, of Cloquet). 

 On the outer dorsal aspect of the wrist, just below the radius, is a depression particu- 

 larly noticeable when the thumb is abducted (Fig. 351, page 341). It is triangular in 



