214 POSTERIOR BRACHIAL REGION. 







Dissection. The integument is to be divided and turned aside, 

 and the fasciae removed in the same manner as for the anterior bra- 

 chial region. 



The Supinator longus muscle is placed along the radial border of 

 the fore-arm. It arises from the external condyloid ridge of the 

 humerus, nearly as high as the insertion of the deltoid, and is inserted 

 into the base of the styloid process of the radius. 



Relations. By its superficial surface with the extensor ossis me- 

 tacarpi pollicis, extensor primi internodii pollicis, and fascia of the 

 fore-arm. By its deep surface with the brachialis anticus, extensor 

 carpi radialis longior, tendon of the biceps, supinator brevis, prona- 

 tor radii teres, flexor carpi radialis, flexor sublimis digitorum, flexor 

 longus pollicis, pronator quadratus, radius, musculo-spiral nerve, 

 radial and posterior interosseous nerve, and radial artery and veins. 



This muscle must be divided through the middle, and the two 

 ends turned to either side to expose the next muscle. 



The Extensor carpi radialis longior arises from the external 

 condyloid ridge below the preceding. Its tendon passes through 

 a groove in the radius, immediately behind the styloid process, 

 to be inserted into the base of the metacarpal bone of the index 

 finger. 



Relations. By its superficial surface with the supinator longus, 

 extensor ossis metacarpi pollicis, extensor primi internodii pollicis, 

 extensor secundi internodii pollicis, radial nerve and fascia of the 

 fore-arm, and posterior annular ligament. By its deep surface with 

 the brachialis anticus, extensor carpi radialis brevior, radius and 

 wrist-joint. 



The Extensor carpi radialis brevior is seen by drawing aside the 

 former muscle. It arises from the external condyle of the humerus, 

 and is inserted into the base of the metacarpal bone of the middle 

 finger. Its tendon is lodged in the same groove on the radius with 

 the extensor carpi radialis longior. 



Relations. By its superficial surface with the extensor carpi 

 radialis longior, extensor ossis metacarpi pollicis, extensor primi 

 internodii pollicis, extensor secundi internodii pollicis, fascia of the 

 fore-arm, and posterior annular ligament. By its deep surface with 

 the supinator brevis, tendon of the pronator radii teres, radius and 

 wrist-joint. By its ulnar border with the extensor communis digi- 

 torum. 



The Extensor communis digitorum arises from the external con- 

 dyle, and divides into four tendons, which are inserted into the second 

 and third phalanges of the fingers. At the metacarpo-phalangeal 

 articulation each tendon becomes narrow and thick, and sends a 

 thin fasciculus upon each side of the joint. It then spreads out and 

 receiving the tendon of the lumbricalis forms a broad aponeurosis, 

 which covers the whole of the posterior aspect of the ringer. At 

 the first phalangeal joint the aponeurosis divides into three slips. 

 The middle slip is inserted into the base of the second phalanx, and 

 the two lateral portions are continued onwards on each side of the 

 joint, to be inserted into the last. Little oblique tendinous slips con- 



