604 



HUMAN ANATOMY. 



Palmaris longus 

 Flexor carpi radialis 

 Pronator radii teres 

 Radial artery 

 Radial nerve 



Brachio- 

 radialis 



Flexor longus pollicis 

 Median nerve 



Ulnar artery 



Flexor sublimis 

 Ulnar nerve 



Skin 



ous at the wrist with the anterior and posterior annular Hgaments. The septa which 

 run in from it to be attached to the sides of the ulna and radius divide the forearm, 

 with the aid of the interosseous membrane, into two musculo-aponeurotic spaces, an 

 antero-external and a posterior (Fig. 583). The former contains numerous muscles 

 and the main vessels and nerves, the latter is almost entirely muscular. 



The interpenetration of these main septa and of the intermuscular fascia by 

 nervo-vascular structures renders them of slight importance in limiting the spread of 

 infectious disease or of collections of blood or pus. But in the not infrequent cases 

 of incised wounds severing the muscles and tendons of this region it may systematize 

 the search for and reunion of the divided structures if the somewhat artificial topog- 

 raphy, as descrified by Tillaux, is borne in mind. The antero-external compart- 

 ment is thus regarded as including four spaces. i. That between the skin and the 

 first muscular layer, — the palmaris, fiexor carpi ulnaris, pronator radii teres, etc., — 

 and containing the -internal cutaneous and musculo-cutaneous nerves, the perforating 

 branches of the radial and ulnar nerves, the superficial veins, and sometimes the 

 ulnar artery when there is a high bifurcation of the brachial. 2. That between the first 

 muscular layer and the flexor sublimis, with the brachio-radialis and short supinator 



externally. This contains 

 Fig. 583. the radial nerve, artery, 



and veins. 3. That be- 

 tween the flexor sublimis 

 and the flexor profundus 

 and flexor longus pollicis. 

 This contains the median 

 nerve and the ulnar nerve 

 and vessels. 4. That be- 

 tween the last-named mus- 

 cles and the interosseous 

 membrane, containing the 

 anterior interosseous ves- 

 sels and the interosseous 

 nerve. 



In the posterior com- 

 partment are to be found, 

 in addition to the exten- 

 sors and the anconeus, 

 only the posterior inter- 

 osseous vessels and nerve 



(Fig- 583). 



Fractures of the neck 

 of the radius (between the head and the tuberosity) are very rare, as it is covered and 

 protected from direct violence by the long and short supinators and the long and 

 short radial extensors. Angular displacement forward is thought to be caused by 

 the action of the biceps on the upper end of the lower fragment. The upper frag- 

 ment is rotated outward by the supinator brevis. Fracture of the radius below its 

 tubercle and above the insertion of the pronator radii teres (a little above the middle 

 of the outer side of the bone) is followed by supination and flexion of the upper frag- 

 ment by the biceps and supinator brevis. The lower fragment is pronated and drawn 

 towards the ulna by the pronators. 



It is well to treat cases of this fracture with the forearm in moderate supination, 

 so as to approximate the fragments and preserve the axis of the bone and the future 

 usefulness of the supinators. 



In fracture of the radius below the insertion of the pronator radii teres the 

 upper fragment is flexed by the biceps, so that its lower end can sometimes be seen 

 and felt on the front of the forearm just above the middle, and is sometimes pronated 

 by the pronator radii teres ; the lower fragment is drawn towards the ulna by the 

 pronator quadratus, aided by the action of the brachio-radialis on the styloid process 

 (Fig. 584). 



In the usual position in which such fractures are treated, the flexion of the elbow 



Extensor 

 carpi rad. 

 long. 

 Radius 



Extensor 

 carpi rad. 

 brev. 



Supinator 



Extensor communis 

 Post, inteross. vessels 

 and nerve 

 Interosseous membrane 



Flexor 



carpi 



ulnaris 



Flexor 

 profundus 



Deep 



fascia 



uperficial 

 fascia 



Extensor carpi ulnaris 

 Extensor ossis metacarpi pollicis Extensor longus pollicis 



Section across middle of right forearm. 



