368 A MANUAL OF ANATOMY 



digital arteries pass forwards in line with the webs of the fingers, 

 and they lie over the interosseous spaces. An incision, therefore, 

 may be made with safety in the palm in the direction of the middle 

 line of a finger, but it should not be carried nearer the wrist than 

 the line indicating the position of the superficial palmar arch. 

 The deep palmar arch lies about | inch nearer the wrist than the 

 superficial. The digital arteries are placed on the lateral aspects 

 of the fingers. 



On the back of the hand the radial tubercle may be felt about 

 the centre of the lower end of the bone, and the heads of the meta- 

 carpal bones, which form the knuckles, are conspicuous when the 

 fingers are flexed. Below and behind the styloid process of the 

 radius there is a well-marked triangular hollow, the base of which 

 is directed upwards, in which, by sinking the finger deeply, pulsa- 

 tion may be felt in the second part of the radial artery in the 

 living subject. At the upper part the tendons of the radial 

 extensors of the wrist may also be felt. The hollow is bounded 

 internally by a prominence formed by the tendon of the extensor 

 longus pollicis, externally by a prominence due to the tendons of 

 the extensor ossis metacarpi pollicis and extensor brevis pollicis, and 

 above by the lower end of the radius. The scaphoid and trapezium 

 lie in its floor, and the radial vein and branches of the radial nerve 

 are in its roof. This hollow is known as the anatomical snuff-box 

 (Cloquet). 



The middle line of the hand, from and towards which abduction 

 and adduction take place, represents a longitudinal line drawn 

 through the centre of the middle finger. 



Superficial Fascia. — ^The superficial fascia, especially over the 

 hollow of the palm, is lobulated, the lobules being separated by 

 fibrous processes which pass between the skin and the central 

 division of the palmar fascia. 



Palmaris Brevis. — ^This is a thin, flat, subcutaneous muscle, of 

 quadrilateral outline, and usually arranged in two or three bundles, 

 separated by fat. 



Origin. — (i) The front of the anterior annular ligament at its 

 lower and inner part, and (2) the inner margin of the central division 

 of the palmar fascia at its upper part. 



Insertion. — ^The integument of the inner border of the hand at its 

 inner part. 



Nerve-supply. — ^The superficial division of the ulnar nerve. 



Action. — ^To draw the integument into which it is inserted towards 

 the middle line of the hand, thus giving rise to a wrinkled depression 

 on the inner border at its upper part. 



The muscle lies in the superficial fascia over the upper part of 

 the hypothenar eminence, and covers the ulnar vessels and nerve, 

 which it guards against pressure. 



Superficial Transverse Ligament. — This ligament is composed of 

 a bundle of transverse fibres, contained within the folds of skin which 

 form the clefts of the four inner fingers. 



