154 SURGICAL ANATOMY OF 



osseous membrane. In the lower third, the tendons of 

 the muscles passing to the wrist lie over the pronator 

 quad rat us, and upon the membrane itself the anterior 

 interosseous vessels and nerves. 



The posterior compartment contains from the surface to 

 the bones, the extensor communis digitorum, slightly 

 covered in above by the extensor carpi radialis longior, 

 and lower down lying along the extensor carpi radialis 

 brevior, extensor minimi digiti, extensor carpi ulnaris, 

 and anconeus. The second layer comprises the extensor 

 ossis metacarpi, primi and secundi internodii pollicis, the 

 extensor indicis, and the posterior interosseous vessels and 

 nerves. The extensors of the thumb will be seen to 

 form a sort of spiral round the lower part of the radius ; 

 they are inclosed in a sheath which is very liable to be 

 the seat of severe teno-synovitis, especially met with in 

 reapers and workmen. 



Relations of the Radial Artery in the Forearm. Sup- 

 posing the vessel to be normal, a line drawn from the 

 middle of the bend of the elbow to the inner side of the 

 styloid process of the radius represents its course in the 

 upper third ; it is concealed by the pronator teres and by 

 the edge of the supinator longus, and lies on the tendon 

 of the biceps, and in a bed of fat and cellular tissue, in 

 relation with some muscular branches of the musculo- 

 spiral nerve, and on the supinator brevis. In the middle 

 third it lies between the tendons of the flexor carpi 

 radialis and supinator longus, having the radial nerve to 

 its outer side, and on the pronator teres and flat head of 

 the flexor sublimis. In the inferior third it has the same 

 tendons on either side, whilst it rests upon the flexor 

 longus pollicis, pronator quadratus, and radius. It is 

 accompanied throughout by vense comites. 



