272 DISSECTION OF THE HAND. 



SECTION V. 



THE PALM OF THE HAND. 



Dissection (fig. 83). The digits being separated and fixed firmly with 

 tacks, the skin is to be reflected from the palm of the hand by means of 

 two incisions. One is to be carried along the centre from the wrist to the 

 fingers ; and the other is to be made from side to side, at the termination 

 of the first. In raising the inner flap, the small palmaris brevis muscle 

 will be seen at the inner margin of the hand ; and its insertion into the 

 skin may be left till the muscle has been learnt. In the fat the ramifica- 

 tions of the small branches (palmar) of the median and ulnar nerves are 

 to be traced. 



The student should remove the fat from the palmaris muscle, and from 

 the strong palmar fascia in the centre of the hand ; and he should take 

 care not to destroy a transverse fibrous band (transverse ligament) which 

 lies across the roots of the fingers. AVhen cleaning the fat from the palmar 

 fascia he will recognize, near the digits, the digital vessels and nerves ; and 

 must be especially careful of two, viz., those of the inner side of the lit- 

 tle finger and outer side of the index finger, which appear farther back 

 than the rest, and are most likely to be injured. By the side of the vessels 

 and nerves to the fingers four slender lumbricales muscles are to be defined. 



Lastly, the skin and the fat may be reflected from the thumb and fingers 

 by an incision along each, in order that the sheaths of the tendons with 

 the collateral vessels and nerves may be laid bare. 



Cutaneous palmar nerves. Some unnamed twigs are furnished to the 

 integument from both the median and ulnar nerves in the hand ; and two 

 named cutaneous nerves ramify in the palm. 



One is an offset of the median nerve (p. 270), and crosses the annular 

 ligament : it extends to about the middle of the palm, and is united with 

 the palmar branch of the ulnar : a few filaments are furnished to the ball 

 of the thumb. 



The other palmar branch is derived from the ulnar nerve (p. 269) ; it 

 has been traced on the ulnar artery to the hand, and its distribution in the 

 palm may be now observed. 



The PALMARIS BREVIS (fig. 83, H ) is a small subcutaneous muscle, about 

 two inches wide, whose fibres are collected into separate bundles. It is 

 attached on the outer side to the palmar aponeurosis, and its fibres are di- 

 rected inwards to join the skin at the inner border of the hand. 



This muscle lies over the ulnar artery and nerve. After it has been ex- 

 amined it may be thrown inwards with the skin. 



Action. Drawing inwards the skin of the inner border of the hand to- 

 wards the centre, it deepens the hollow or cup of the palm. 



The palmar fascia or aponeurosis consists of a central and two lateral 

 parts ; but the lateral, which cover the muscles of the thumb and little 

 finger, are so thin as not to require separate notice. 



The central part is a strong, white layer, which is pointed at the wrist, 

 but is expanded towards the fingers, where it nearly covers the palm of the 

 hand. Posteriorly the fascia receives the tendon of the palmaris longus, 

 and is connected to the annular ligament ; and anteriorly it ends in four 



