260 DISSECTION OF THE FRONT OF THE FOREARM. 



SECTION IV. 



THE FRONT OF THE FOREARM. 



Position. The limb is to be placed with the palm of the hand upper- 

 most ; and the marking of the surface, and the projections of the bone, are 

 first to be noted. 



Surface-marking. On the anterior aspect of the forearm are two lateral 

 depressions, corresponding with the position of the main vessels. The 

 external is placed over the radial artery, and inclines towards the middle 

 of the limb as it approaches the elbow. The internal groove is evident 

 only beyond the middle of the forearm, and points out the place of the 

 ulnar artery. 



The bones (radius and ulnar) are sufficiently near the surface to be 

 traced in their whole length : each ends below in a point the styloid 

 process ; and that of the radius is the lowest. A transverse line separates 

 the forearm from the hand, and the articulation of the wrist is about an 

 inch above it. 



On each side of the palm of the hand is a lateral projection ; the exter- 

 nal of these (thenar) is formed by muscles of the thumb, and the internal 

 (hypo-thenar) by muscles of the little finger. Between the projections is 

 the hollow of the palm, which is pointed towards the wrist. Two trans- 

 verse lines are seen in the palm, but neither reaches completely across it : 

 the anterior one will direct to the line of the articulations between the 

 metacarpus and the phalanges, but is about a quarter of an inch behind 

 the three inner joints when the fingers are extended. 



The superficial palmar arch of arteries reaches forwards a little way 

 into the hollow of the hand, and its position may be marked by a line 

 across the palm from the root of the thumb, when that digit is placed at a 

 right angle to the hand. 



Transverse lines are seen on both aspects of the joints of the thumb and 

 fingers. The lines on the palmar surface of the fingers may be used to 

 detect the articulations of the phalanges. Thus the joint between the 

 metacarpal phalanx and the next will be found about a line in front of the 

 chief transverse groove ; whilst the articulation between the last two pha- 

 langes is situate about a line in front of the single mark. 



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

 carried through the skin along the middle of the front of the 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 integ- 

 ument 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 ; they 

 have the following position, and most of them have been partly dissected : 

 Along the inner side, in front of the forearm with the ulnar veins, is the 

 continuation of the internal cutaneous nerve ; and near the wrist there is 



