EXTENSOR CARPI RADIALIS. 



241 



Ft?. 100." 



The EXTENSOR CARPI RADIALIS 

 LONGIOR arises from the external 

 condyloid ridge below the preced- 

 ing, and from the intermuscular 

 fascia. Its tendon passes through 

 a groove in the radius, immediately 

 behind the styloid process, to be 

 inserted into the base of the meta- 

 carpal 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, fascia of the fore- 

 arm, and posterior annular liga- 

 ment. 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 intermuscular fascia, and is in- 

 serted into the base of the metacar- 

 pal 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 ra- 

 dialis longior, extensor ossis meta- 

 carpi pollicis, extensor prinii in- 

 ternodii pollicis, extensor secundi 

 internodii pollicis, fascia of the 

 forearm, and posterior annular liga- 

 ment. By its deep surface with the 



* The superficial layer of muscles of the posterior aspect of the fore-arm. 



I. The lower part of the biceps. 2. Part of the brachialis anticus. 3. The 

 lower part of the triceps, inserted into the olecranon. 4. The supinator longus. 

 5. The extensor carpi radialis longior. 6. The extensor carpi radialis brevior. 

 /. The tendons of insertion of these two muscles. 8. The extensor communis 

 digitorum. 9. The extensor minimi digiti. 10. The extensor carpi ulnaris. 



II. The anconeus. 12. Part of the flexor carpi ulnaris. 13. The extensor 

 ossis metacarpi and extensor primi internodii muscle, lying together. 14. The 

 extensor secundi internodii ; its tendon is seen crossing the two tendons of the 

 extensor carpi radialis longior and brevior. 15. The posterior annular ligament. 

 The tendons of the common extensor are seen upon the back of the hand, and 

 their mode of distribution on the dorsum of the fingers. 



