OF THE HAND. 315 



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 radialis and 

 ulnaris. The common Extensor of the fingers, the Extensors of the thumb, 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 con- 

 tinuing their action, they assist in extending the forearm. The Extensors of the 

 thumb may assist in supinating the forearm, when this part of the hand has been 

 drawn inwards towards the palm, on account of the oblique direction of the tendons 

 of these muscles. 



MUSCLES AND FASCIAE OF THE HAND. 



Dissection (fig. 168). 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 these 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 and ulnar nerves. It has inserted into its 

 upper and inner part, the tendon of the Flexor carpi ulnaris ; and has, arising 

 from it below, the small muscles of the thumb and little finger. It is pierced by 

 the tendon of the Flexor carpi radialis ; and, beneath it, pass the tendons of the 

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

 the median nerve. There are two synovial membranes beneath this ligament ; one 

 of large size, inclosing the tendons of the Flexor sublimis and Flexor profundus ; 

 and a separate one for the tendon of the Flexor longus pollicis ; the latter is also 

 large and very extensive, reaching from above the wrist to the extremity of the 

 last phalanx of the thumb. 



The Posterior Annular Liga- 

 ment is a Strong fibrous band, Fig. 176. -Transverse section through the Wrist, show- 

 extending transversely across in o the Posterior Annnlar Ligament, and the canals 



the back of the wrist, and con- for the passage of the ExttJllsor Tendous ' 



tinuous with the fascia of the 

 forearm. 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; ex- 

 ternally, 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 presents six com- 

 partments for the passage of &T - ^^-' 

 tendons, each, of which is. lined 

 by a separate synovial mem- 

 brane. These are, from without inwards 1. On the outer side of the styloid pro- 

 cess for the tendons of the Extensor ossis metacarpi pollicis, and Extensor primi 

 internodii pollicis. 2. Behind the styloid process, for the tendons of the Extensor 

 carpi radialis longior and brevior. 3. Opposite the outer side of the posterior 

 surface of the radius, for the tendon of the Extensor secundi internodii pollicis. 



