APONEUROSIS OF FOREARM. 263 



from it. Close to the pisiform bone there is an aperture through which 

 the ulnar vessels and nerve enter the fat of the hand. Behind the wrist 

 it is thickened by transverse fibres, giving rise to the posterior annular 

 ligament ; but on the back of the hand and fingers the fascia becomes 

 very thin. 



Dissection. The skin is to be replaced on the back of the forearm and 

 hand, in order that the denuded parts may not become dry. Beginning 

 the dissection on the anterior surface of the limb, let the student divide the 

 aponeurosis as far as the wrist, and take it away with the cutaneous vessels 

 and nerves, except the small palmar cutaneous offsets of the median and 

 ulnar nerves near the wrist. In cleaning the muscles it will be impossible 

 to remove the aponeurosis from them at the upper part of the forearm 

 without detaching muscular fibres. 



In front of the elbow is the hollow, already partly dissected, between 

 the two masses of muscles arising from the inner and outer sides of the 

 humerus. The space should be carefully cleaned, so as to display the 

 brachial and forearm vessels, the median nerve and branches, the musculo- 

 spiral nerve, and the recurrent radial and ulnar arteries. 



In the lower half of the forearm a large artery, radial, is to be laid bare 

 along the radial border ; and at the ulnar side, close to the annular liga- 

 ment, the trunk of the ulnar. artery will be recognized, as it becomes 

 superficial. These vessels and their branches should be carefully cleaned ; 

 but the collateral muscles should be fixed with stitches to prevent their 

 displacement. 



The anterior annular ligament of the wrist, which arches over the ten- 

 dons passing to the hand, is next to be defined. This strong band is at 

 some depth from the surface; and whilst the student removes the fibrous 

 tissue superficial to it, he must take care of the small branches of the 

 median and ulnar nerves to the palm of the hand. The ulnar vessels and 

 nerve pass over the ligament, and will serve as a guide to its depth. 



Hollow in front of the elbow (fig. 80). This hollow corresponds with 

 the popliteal space at the knee, and is situate between the inner and the 

 outer muscles of the forearm. The interval is somewhat triangular in 

 shape, and the wider part is towards the humerus. It is bounded on the 

 outer side by-the supinator longus muscle, and on the inner side by the 

 pronator teres. The aponeurosis of the limb is stretched over the space ; 

 and the bones, covered by the brachialis anticus and supinator brevis, form 

 the deep boundary. 



Contents. In the hollow are lodged the termination of the brachial 

 artery with its veins, and the median nerve ; the inusculo-spiral nerve ; the 

 tendon of the biceps muscle ; and small recurrent vessels, with much fat 

 and a few glands. 



These several parts have the following relative position : The tendon of 

 the biceps is directed towards the outer boundary to reach the radius ; on 

 the outer side, concealed by the supinator longus muscle, is the muscnlo- 

 spiral nerve. Nearly in the centre of the space are the brachial artery and 

 veins and the median nerve, the nerve being internal ; but as the artery is 

 inclined to the outer part of the limb, they soon become distant from one 

 another about half an inch. The brachial artery divides here into two 

 trunks radial and ulnar ; and the recurrent radial and ulnar branches 

 appear in the space, one on the outer and the other on the inner side. 



Two or three lymphatic glands lie on the sides of the artery, and one 

 below its point of splitting. 



