OF THE HAND. 393 



flexor muscles. The Anconeus assists the Triceps in extending the forearm. 

 The Supinator Longus and Supinator Brevis are the supinators of the forearm 

 and hand ; the former muscle more especially acting as a supinator when the 

 limb is pronated. When supination has been produced, the Supinator Longus, 

 if still continuing to act, flexes the forearm. The Extensor Carpi Eadialis 

 Longior and Brevior, and Extensor Carpi Ulnaris muscles, are the extensors of 

 the wrist ; continuing their action, they serve to extend the forearm upon -the 

 arm ; they are the direct antagonists of the Flexor Carpi Eadialis and Flexor 

 Carpi Ulnaris. The common Extensor of the fingers, the Extensors of the 

 t-humb, and the Extensors of the index and little fingers, serve to extend the 

 phalanges into which they are inserted; and are the direct antagonists of the 

 Flexors. By continuing their action, they assist in extending the forearm. 

 The Extensors of the thumb, in consequence of the oblique direction of their 

 tendons, assist in supinating the forearm, when the thumb has been drawn 

 inwards towards the palm. 



MUSCLES AND FASCIA OF THE HAND. 



Dissection (Fig. 235). 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 centre of the middle finger. The anterior and posterior annular 

 ligaments, and the palmar fascia, should first 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 pisiform bone, and unciform process of the unciform; and 

 externally, to the tuberosity of the scaphoid, and ridge on the trapezium. It is 

 continuous, above, with the deep fascia of the forearm, and below, with the 

 palmar fascia. It is crossed by the tendon of the Palmaris Longus, by the 

 ulnar vessels and nerve, and the 



cutaneous branches of the median Fig. 243. Transverse Section through the 

 and ulnar nerves. It has inserted Jurist, f mg the Annular Ligaments and the 

 . , ., , . Canals for the Passage of the lendons. 



into its upper and inner part the 



greater part of the tendon of the 

 Flexor Carpi Ulnaris; and has, aris- 

 ing from it below, the small muscles 

 of the thumb and little finger. It is 

 pierced by the tendon of the Flexor 

 Carpi Eadialis ; and, beneath it, pass 

 the tendons of the Flexor Sublimis 

 and Flexor Profundus Digitorum, the 

 Flexor Longus Pollicis, and the me- 

 dian nerve. There are two synovial 

 membranes beneath this ligament: 



1 1 .-I 



one of large size, inclosing the ten- 

 dons of the Flexor Sublimis and 

 Flexor Profundus; and a separate one for the tendon of the Flexor Longus 

 Pollicis, which is also very extensive, reaching from above the wrist to the 

 extremity of the last phalanx of the thumb. 



The Posterior Annular Ligament is a strong fibrous band, extending trans- 

 versely across the back of the wrist, and continuous with the fascia of the fore- 

 arm. It forms a sheath for the extensor tendons in their passage to the fingers, 

 being attached, internally, to the ulna, the cuneiform and pisiform bones, and 

 palmar fascia; externally, to the margin of the radius: and in its passage across 

 the wrist, to the elevated ridges on the posterior surface of the radius. It pre- 

 sents six compartments for the passage of tendons, each of which is lined 

 by a separate synovial membrane. These are, from without inwards: 1. On 

 the outer side of the styloid process for the tendons of the Extensor Ossis Meta- 



