26 THE ANATOMY OF THE HORSE. 



middle in order to follow the anterior radial artex'j ; and by dissecting 

 deeply down in front of the ^Ibow, between the brachialis anticus and 

 the extensor metacarpi niagniis, the artery will be found to meet the 

 musculo -spiral nerve. The extensor metacarpi magnus is to be cut 

 about its middle and carefully reflected in order to follow the artery, 

 which lies in relation to the deep face of the muscle ; and the extensor 

 pedis is to be similarly reflected to trace the termination of the mus- 

 culo-spiral nerve. 



The Anteriou Radial Artery (Plate 8) is the smaller terminal 

 branch of the brachial. It separates at an acute angle from the pos- 

 terior radial, and passes forwards beneath the biceps and then beneath 

 the brachialis anticus. It meets the musculo-spiral nerve in the inter- 

 space between the brachialis anticus and the extensor metacarpi magnus, 

 and afterwards descends on the anterior surface of the radius, where it 

 is covered by the last-mentioned muscle. It terminates at the carpus 

 by anastomosing inwardly with branches from the posterior radial, and 

 outwardly with the interosseous artery of the fore- arm. It supplies 

 articular branches to the elbow, and muscular branches to the muscles 

 on the front of the fore-arm. 



The Interosseous Artery of the fore-arm (Plate 7) is a branch 

 given off" by the median at the back of the fore -arm. It comes out- 

 wards through the radio -ulnar arch, and descends along the extensor 

 suffraginis, terminating in slender branches in front of the carpus. 

 It supplies articular branches to the elbow ; the nutrient artery of the 

 radius ; and miiscular twigs to the extensor suffraginis, extensor pedis, 

 and extensor metacarpi obliquus. 



The anterior radial and interosseous arteries are, generally, compara- 

 tively slender vessels, but they are liable to some variation in size and 

 distribution, and the one may partly supplant the other. 



Veins. Satellite veins of the same names run in company with the 

 foregoing arteries. 



The MuscuLO-spiUAL Nerve in the fore-arm (Plate 8). In the dissec- 

 tion of the axilla and arm, this nerve has already been seen as a large 

 trunk descending fi-om the brachial plexus, and taking a spiral course be- 

 hind the humerus. It reaches the front of the elbow, where it meets the 

 radial artery in the interspace between the brachialis anticus inwardly, 

 and the origin of the extensor metacarpi magnus outwardly. It here 

 gives off" branches to the extensor metacarpi magnus, extensor pedis, 

 extensor suff"raginis, and flexor metacarpi externus ; and, much 

 reduced in size, it descends between the shaft of the radius and the 

 extensor pedis, and terminates in the extensor metacarpi obliquus. The 

 nerve to the flexor metacarpi externus is furnished after the branches to 

 the extensor pedis, and passing outwards between the latter muscle and 

 the bone, it penetrates its muscle at the radio-ulnar arch. 



