THE HAND. 



401 



Dissection (Fig. 228). Make a transverse incision across the front of the wrist, and a 

 second across the heads of the metacarpal bones : connect the two by a vertical incision in the 

 middle line, and continue it through the cen- 

 tre of the middle finger. The anterior and 

 posterior annular ligaments and the palmar 

 fascia should then be dissected. 



The Anterior Annular Ligament is 

 a strong, fibrous band which arches 

 over the carpus, converting the deep 

 groove on the front of the carpal 

 bones into a canal, beneath which 

 pass the flexor tendons of the fingers. 

 It is attached, internally, to the pisi- 

 form bone and the hook of the unci- 

 form bone, and externally to the 

 tuberosity of the scaphoid and to the 

 inner part of the anterior surface and 

 the ridge on the trapezium. It is 

 continuous, above, with the deep 



fascia of the forearm, of which it may be regarded as a thickened portion, and, 

 below, with the palmar fascia. It is crossed by the ulnar vessels and nerve and 

 the cutaneous branches of the median and ulnar nerves. At its outer extremity 

 is the tendon of the Flexor carpi radialis, which lies in the groove on the trapezium 

 between the attachments of the annular ligament to the bone. It has inserted into 

 its anterior surface a part of the tendon of the Palmaris longus and part of the 

 tendon of the Flexor carpi ulnaris, and has arising from it, below, the small 



FIG. 238. Transverse section through the wrist, show- 

 ing the annular ligaments and the canals for the passage 

 of the tendons. 



ANNULAR LIGAMENT 

 FLEXOR LONGUS POLLICIS. 

 FLEXOR CARPI RADIALIS 

 MUSCLES OF THUMB.^ \ 



1st Metacarpal 



EXT. PRIM 



INTERNOD. 



POLL. 



EXT. SEC 



INTERNOD 



POLL 



Trapezium: 



Radial vessels. 



EXT. CARP. RAD. LO" 



Trapesoid. 



EXTENSOR CARPI RADIALIS 

 BREVIOR. 



Median nerve. 



vessels. 



ALMARIS BREVIS. 



MUSCLES OF 

 LITTLE 

 FINGER. 



EXT. CARPI 

 ULNARIS. 



EXTENSOR 

 MINIMI 

 DIGIT). 

 EXTENSOR 

 OMMUNIS 

 DIGITORUM. 

 EXTENSOR INDICIS. 



OK iiiniiniiin. 



FIG. 239. Transverse section through the carpus, showing the relative positions of the tendons, vessels, and 

 nerves. (Henle.) 



muscles of the thumb and little finger. Beneath it pass the tendons of the Flexor 

 sublimis and profundus digitorum, the Flexor longus pollicis, and the median 

 nerve. 



The Synovial Membranes of the Flexor Tendons at the Wrist. There are two 

 synovial membranes which enclose all the tendons as they pass beneath this lig- 

 ament one for the Flexor sublimis and profundus digitorum, the other for the 

 Flexor longus pollicis. They extend up into the forearm for about an inch above 

 the annular ligament, and downward about halfway along the metacarpal bone, 

 where they terminate in a blind diverticulum around each pair of tendons, with the 

 exception of that of the thumb and those of the little finger in these two digits 

 the diverticulum is continued on, and communicates with the synovial sheath of the 

 tendons in the fingers. In the other three fingers the synovial sheath of the 



26 



