480 THE MUSCLES AND FASCIAE 



to the glenoid (anterior metacarpophalangeal) ligament, and is easily closed by two fine cat- 

 gut sutures passed vertically i. e., from the dorsal to the palmar wall. Opposite the shafts 

 of the first and second phalanges, however, there is much difficulty in effecting closure, since 

 the sheath is united to the periosteum, and that membrane is very thin. In these situations 

 the periosteum should be stripped up a little from the palmar aspect of the bone, and the orifice 

 of the tube secured by two fine sutures passed either vertically or transversely, as may appear 

 the more convenient,. This stripping off of periosteum should be effected before the bone is 

 divided." 1 



9. The Radial Region (Figs. 356, 359). 



Brachioradialis [Supinator longus]. Extensor carpi radialis longior. 



Extensor carpi radialis brevior. 



Dissection. Divide the integument in the same manner as in the dissection of the anterior 

 brachial region, and, after having examined the cutaneous vessels and nerves and deep fascia, 

 remove all those structures. The muscles will then be exposed. The removal of the fascia 

 will be considerably facilitated by detaching it from below upward. Great care should be 

 taken to avoid cutting across. the tendons of the muscles of the thumb, which cross obliquely 

 the larger tendons running down the back of the radius. 



The Brachioradialis (m. brachioradialis, formerly Supinator longus) (Fig. 356) 

 is the most superficial muscle on the radial side of the forearm; it is fleshy for the 

 upper two-thirds of its extent, and becomes tendinous below. It arises from 

 the upper two-thirds of the external supracondylar ridge of the humerus, and from 

 the external intermuscular septum, being limited above by the musculospiral 

 groove. The fibres terminate above the middle of the forearm in a flat tendon, 

 which is inserted into the outer side of the base of the styloid process of the radius. 



Relations. By its superficial surface, with the integument and fascia for the greater part of 

 its extent; near its insertion it is crossed by the Extensor ossis metacarpi pollicis and the 

 Extensor brevis pollicis; by its deep surface, with the humerus, the Extensor carpi radialis 

 longior and brevior, the insertion of the Pronator teres, and the Supinator [brevis]; by its 

 inner border, above the elbow, with the Brachialis anticus, the musculospiral nerve, and the 

 radial recurrent artery; and in the forearm with the radial vessels and nerve. 



The Extensor carpi radialis longior (m. extensor carpi radialis longus) (Fig. 

 359) is placed partly beneath the preceding muscle. It arises from the lower 

 third of the external supracondylar ridge of the humerus, and from the external 

 intermuscular septum by a few fibres from the common tendon of origin of the 

 Extensor muscles of the forearm. The fibres terminate at the upper third of 

 the forearm in a flat tendon, which runs along the outer border of the radius, 

 beneath the Extensor tendons of the thumb ; it then passes through a groove com- 

 mon to it and the Extensor carpi radialis brevior, immediately behind the styloid 

 process, and is inserted into the base of the metacarpal bone of the index finger, 

 on its radial side. 



Relations. By its superficial surface, with the Brachioradialis and fascia of the forearm; its 

 outer side is crossed obliquely by the Extensor tendons of the thumb ; by its deep surface, with the 

 elbow-joint, the Extensor carpi radialis brevior, and back part of the wrist. 



The Extensor carpi radialis brevior (m. extensor carpi radialis brevis) (Fig. 

 359) is shorter, as its name implies, and thicker than the preceding muscle, beneath 

 which it is placed. It arises from the external condyle of the humerus by a tendon 

 common to it and the three following muscles; from the external lateral ligament 

 of the elbow-joint, from a strong aponeurosis which covers its surface, and from 



1 Operative Surgery. By Sir Frederick Treves. 



