98 



DISSECTION OF THE UPPER LIMB. 



oblique 

 ligament. 



The lower 

 end after. 



Kind of 

 motion of 

 radius : 



pronation, 



supination 



axis of 

 motion ; 



use of 



ligaments : 



in fracture 

 motion 



The oblique ligament (fig. 39, 3 ) is a slender band above the 

 interosseous membrane, the fibres of which have a direction opposite 

 to those of the membrane. By one end it is fixed to the lower end 

 of the coronoid process, and by the other to the radius below 

 the tnberosity. The ligament divides into two the space above 

 the interosseous membrane. Oftentimes this band is not to be 

 recognised. 



The lower radio-ulnar articulation cannot be well seen till after 

 the examination of the wrist-joint. 



Movement of the radius. The radius moves forwards and 

 backwards upon the ulna. The forward motion, directing the 

 palm of the hand backwards, is called pronation ; and the back- 

 ward movement, by which the palm of the hand is turned to the 

 front, is named supination. 



In pronation, the upper end of the bone rotates within the band 

 of the orbicular ligament without shifting its position to the ulna. 

 The lower end, on the contrary, moves over the ulna from the outer 

 to the inner side, describing nearly half a circle ; and the shaft 

 crosses obliquely that of the ulna. 



In supination, the lower end of the radius turns backwards over 

 the ulna ; the shafts come to be placed side by side, the radius 

 being external ; and the upper end rotates from within out in its 

 circular band. 



In these movements the radius revolves round an axis, internal 

 to the shaft, which is prolonged upwards through the neck and 

 head of the bone, and downwards through the styloid process of 

 the ulna. 



The upper end of the bone is kept in place by the orbicular 

 ligament ; the lower end by the triangular nbro-cartilage ; and the 

 shafts are united by the interosseous ligament, which is tightened 

 in supination, and relaxed in pronation. 



In fracture of either bone the movements cease ; in the one case 

 because the radius cannot be moved unless it is entire ; and in the 

 other because the broken ulna cannot support the revolving radius. 



THE WRIST-JOINT. 



bisection. Dissection. To see the ligaments of the wrist-joint, the tendons 

 and the annular ligaments must be removed from both the front 

 and back ; and the fibrous structures and the small vessels should 

 be taken from the surface of the ligaments. 



THE WRIST- JOINT (radio-carpal articulation; fig. 41). The 

 lower end of the radius, and the first row of the carpal bones, 

 except the pisiform, enter into this joint. Four ligaments connect 

 the bones, viz., anterior and posterior, and two lateral. The ulna 

 is shut out from the articulation by a piece of fibro-cartilage. 



The external lateral ligament is a short band, which passes 

 from the styloid process of the radius to the outer part of the 

 scaphoid bone. 



Bones form- 

 ing wrist- 

 joint 

 united by 



external 

 lateral, 



