78 Anatomy Applied to Medicine and Surgery. 



ulnaris muscle on its inner side, and is gradually ap- 

 proached by the ulnar artery. The radial nerve is the 

 continuation downwards of the musculo-spiral and lies on 

 the radial side of the radial artery. It has the same rela- 

 tions as the radial artery, excepting that it does not 

 rest on the biceps tendon above nor on the pronator 

 quadratus below. The reason it does not rest on the latter 

 muscle is that it passes from the front of the forearm, out- 

 wards under the supinator longus tendon, at a point about 

 three inches above the wrist joint, to supply the super- 

 ficial structures of the lower part of the back of the fore- 

 arm below the musculo-cutaneous nerve. The. posterior 

 mterosseous nerve, the other terminal branch of the musculo 

 -spiral, winds around to the back of the forearm through 

 the fibres of the supinator brevis and passes down between 

 the superficial and deep muscles of the posterior surface. 

 Below the extensor ossis metacarpi pollicis it passes 

 beneath the extensor secundi internodii, and, running 

 down on the interosseous membrane, terminates at the 

 back of the wrist joint in a gangliform enlargement. It 

 supplies the back of the wrist and all the posterior and 

 radial muscles excepting the supinator longus, the exten- 

 sor carpi radialis longior and the anconeous, which are 

 supplied by the musculo-spiral nerve. 



Landmarks. Bloodvessels. The superficial land- 

 mark for the radial artery is a line drawn from a point 

 half an inch below the centre of the bend of the 

 elbow, to the inner side of the fore part of the styloid 

 process of the radius, or, since the direction of the 

 radial is, more or less, a continuation downwards of the bi- 

 ceps tendon, the course of the artery would correspond to 

 a line drawn, downwards, from the point where the biceps 

 tendon ceases to be felt in the triangular space in tront of 

 the elbow and terminating at the styloid process as 



