EXTENSOR OOMMUNIS DIGITORUM. 



215 



nect the tendons of the middle, ring, and little finger as they cross 

 the back of the hand. 



Fig. 86.* 



Fig. 87.t 



Relations. By its superficial surface with the fascia of the fore- 

 arm and back of the hand, and with the posterior annular ligament. 

 By its deep surface with the supinator brevis, extensor ossis meta- 



* The superficial layer of muscles of the posterior aspect of the fore-arm. 1. 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. 7. The tendons of insertion 

 of these two muscles. 8. The extensor communis digitorum. 9. The extensor minimi 

 digiti. 10. The extensor carpi ulnaris. 11. 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 annu- 

 lar 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. 



t The deep layer of muscles on the posterior aspect of the fore-arm. 1. The lower 

 partofthchumerus. 2. The olecranon. 3. The ulna. 4. The aneoneus muscle. 5. 

 The supinator brevis muscle. 6. The extensor ossis metacarpi pollicis. 7. The exten- 

 sor primi internodii pollicis. 8. The extensor secundi internodii pollicis. fl. The 

 extensor indicis. 10. The first dorsal interopscous muscle. The other three dorsal 

 interossei are seen between the metacarpul bones of their respective fingers. 



