SHOULDER, ARM, FOREARM, HAffD. POSTERIOR I'.lKT. ; l5 . 



<l\le; (2) the posterior surface of the ulna; (3) posterior border of the ulna, in 

 common with the flexor carpi ulnaris. Dissection of this latter muscle requires 



The deep group of muscles and their origin (Figs. 245 and 246) 

 I. The extensor loii-us pollicis ulna ami intcrosseous membrane. 



Bupinator brevis 



Extensor osi metacarpi polliois 



Extensor brevis pollicis 

 Extensor lonffus polliols 



Radial extensors 



Flexor carpi ulnaris 



Flexor profundus dtgitoruro 



Extensor indiols 



Extensor carpi ulnaris 



FIG. 245. THE DKEP LAYKR OF THE BACK OF THE FOREARM. 



2. The extensor brevis pollicis radius and interosseous membrane. 



3. The extensor ossis metacarpi pollicis radius interosseous membrane and 

 ulna. 



4. The extensor indicis from the ulna. 



In view of the special importance of the three extensors of the thumb and the 



