368 



MUSCLES ON THE BACK OF THE FOREARM. 



Fig. 96.< 



Inserted into the outer side of the infe- 

 rior extremity of the radius. 



Use. To roll the radius outwards, and 

 consequently the palm of the hand up- 

 wards. 



2. Extensor Carpi Radialis Longior, 

 Arises, broad, thin, and fleshy, immedi- 

 ately below the supinator radii longus, from 

 the lower part of the external ridge of the os 

 humeri, above its external condyle. 



Inserted, by a round tendon, into the pos- 

 terior and upper part of the metacarpal bone 

 that sustains the fore-finger. 



Use. To extend and bring the hand back- 

 wards. 



3. Extensor Carpi Radialis Brevior, 

 Arises, tendinous, from the external con- 

 dyle of the os humeri, and from the ligament 

 that connects the radius to it, and runs along 

 the outside of the radius. 



Inserted, by a round tendon, into the 

 upper and back part of the metacarpal bone 

 that sustains the middle finger. 



Use. To assist the last mentioned muscle. 



4. Extensor Carpi Ulnaris, 

 Arises, tendinous from the external condyle of the os humeri, 



* The superficial layer of muscles on 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 supinaver longus, 

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

 7. 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 lingers. 



