SURFACE-MARKING OF FOREARM. 55 



On each side of the palm of the hand is a large projection ; the surface of 

 external of these (thenar) is formed by muscles of the thumb, and P al "J of the 

 the internal (hypothenar) by muscles of the little finger. At the 

 upper end of the latter the prominent pisiform bone is easily felt ; 

 and towards the outer side of the wrist, below the end of the radius, 

 the tuberosity of the scaphoid bone is to be recognised. Between 

 the muscular eminences is the hollow of the palm, which is pointed 

 towards the wrist. Two transverse lines are seen in the palm, but 

 neither reaches completely across it ; they result from the bending 

 of the fingers at the metacarpo-phalangeal articulations, but the 

 lower one is nearly half an inch above the three inner joints when 

 the fingers are extended. 



The position of the superficial palmar arch of arteries is marked Position of 

 by the middle third of a line drawn across the palm from the root 

 of the thumb when that digit is placed at a right angle to the hand ; 

 the deep palmar arch is about a finger's breadth nearer the wrist. 



Transverse lines on the palmar aspects of the thumb and fingers Surface of 

 correspond to the articulations of the phalanges ; but while the 

 middle and lower ones are a little above the two interphalangeal 

 articulations, the upper one is fully half an inch below the metacarpo- 

 phalangeal joint. 



Dissection. With the limb lying flat on the table, an incision Dissection 

 is to be carried through the skin along the middle of the front of the the^k^, 6 

 forearm, as far as an inch beyond the wrist ; and at its termination 

 a transverse one is to cross it. The skin is to be reflected carefully 

 from the front and back of the forearm, without injury to the 

 numerous superficial vessels and nerves beneath : and it should be 

 taken also from the back of the hand by prolonging the ends of 

 the transverse cut along each margin to a little beyond the knuckles. 

 The whole of the forefinger should have the integument removed 

 from it, in order that the nerves may be followed to the end. 



The superficial vessels and nerves can be now traced in the fat : Seek the 

 they have the following position, and most of them have been partly vesS^nd 

 dissected : along the inner side, with the ulnar veins, is the con- nerves in 

 tinuation of the internal cutaneous nerve ; and near the wrist there 

 is occasionally a small offset from the ulnar nerve. On the outer 

 side, with the radial vein, is the superficial part of the musculo- 

 cutaneous nerve. 



Close to the hand, in the centre of the forearm, and inside the 

 tendon of the flexor carpi radialis, which can be rendered tense by 

 extending the wrist, the small palmar branch of the median nerve 

 should be sought beneath the fat. On the ulnar artery, close out- 

 side the pisiform bone, a small palmar branch of the ulnar nerve is 

 to be looked for. 



Near the middle of the back of the forearm the large external behind, 

 cutaneous branch of the musculo-spiral nerve is to be traced onwards ; 

 and offsets are to be followed to this surface of the limb from the 

 nerves in front on either side. 



On the posterior part of the hand is a plexus of superficial veins, and on the 

 Winding back below the ulna is the dorsal branch of the ulnar 



