THE FOREARM. 303 



be opened. The line of the joint runs from i. 25 cm. below the lateral (ext. ) condyle to 

 2.5 cm. below the medial (int.) condyle and is most readily recognized on the outer 

 side, hence the division of the ligaments is to be made from the outer toward the 

 inner side. The point at which to enter the knife is to be found by first feeling the 

 head of the radius in the pit below the lateral (external) condyle posteriorly and then 

 by pressure just above the head recognizing the groove between the upper edge of 

 the head and capitellum. The knife passes directly traversely along between the 

 head of the radius and capitellum, then across the inner portion of the trochlea and is 

 then directed downward and inward around the projecting inner portion of the 

 trochlea. Division of the internal lateral ligament allows the forearm to be bent back 

 and the triceps attachment becomes exposed and can be divided from the front. The 

 appearance of the stump will depend on the manner in which the flaps have been cut. 



On each side will be the muscular masses from the internal and external con- 

 dyles. Between them will be the tendons of the biceps and brachialis anticus. The 

 median and ulnar nerves are to be found, the former to the inner side of the biceps 

 tendon and the latter behind the medial (internal) condyle. They are to be short- 

 ened. The radial (musculospiral) has already divided into its superficial (radial) and 

 deep (posterior interosseous) branches. 



The ulnar and radial arteries will probably be found divided well anterior on the 

 face of the stump. Some bleeding may be present from the terminal branches of the 

 profunda in front of the lateral condyle, from the superior ulnar collateral (inferior 

 profunda) behind the medial condyle, or from the interosseous or recurrent branches. 

 It is usually not necessary to apply ligatures to the larger superficial veins. 



THE FOREARM. 



The forearm is intimately associated with the functions of the hand. It serves 

 as a sort of pedestal or support, enabling the hand to be carried away from the body, 

 and, by possessing certain movements of its own, those of pronation and supination, 

 it increases greatly the range and character of the movements which the hand 

 is capable of executing. The hand is the essential part of the upper extremity and 

 the forearm is subsidiary. Hence we find that, like the neck, the forearm possesses 

 nerves and blood-vessels much larger than its own proper functions would require and 

 which are destined for the more important parts beyond. It is composed of two 

 bones, the radius and the ulna, which act as the bony support of the part, of a few 

 muscles which move these bones and many more which move the hand and fingers 

 beyond, and of certain nerves and blood-vessels 'that not only supply it but also the 

 parts beyond. 



BONES OF THE FOREARM. 



The forearm contains two bones, instead of one as in the arm. One of these 

 bones, the ulna, is directly continuous with the humerus; the other, the radius, is 

 continuous with the hand. In other words, the ulna is associated with the move- 

 ments of the arm, and the radius with those of the hand. The large end of the ulna 

 articulates with the humerus and its small end is at the wrist, while the large end of 

 the radius is articulated with the hand and its small end with the humerus. 



The ulna is the bone which acts mainly as a support. It articulates with the 

 humerus by a pure hinge-joint; hence its only motion is one of extension and flexion. 

 It is the fixed bone and does not take part in the movements of pronation and supi- 

 nation, but serves as an anchoring part for the attachment of the muscles which move 

 the radius as well as the hand. At its upper extremity it has attached to it the 

 brachialis anticus, triceps, and anconeus muscles, which flex and extend it. 



At its upper extremity on its outer side is the lesser sigmoid cavity for the articu- 

 lation of the radius. Its lower extremity ends in a head tipped with a styloid process. 

 The ulna gradually decreases in size from above downward until its lower fourth is 

 reached, when it is slightly enlarged to end in the head. At its lower end, the lateral 

 aspect of the head of the ulna rests in a cavity in the radius to allow of the movements 

 of pronation and supination (Fig. 318). 



