282 



COMPARATIVE ANATOMY 



brachialis bend the elbow. The biceps brachii is also the most powerful 

 supinator of the forearm. 



Muscles of the Forearm and Hand. There are many more muscles 

 in the forearm than in the upper arm, and the diversity of function is also 

 much greater. Two groups are distinguished, a radio-dorsal which 

 straightens the wrist and supinates the forearm, and an ulno-volar group 



GASTROCNEMIUS 

 FLEX. OIGITORUM, 

 LONGUS. ^ 



EXT. CARPI ULNARIS ^ 

 SUPINATORr-^^Ci 



FLEX. DIGITORUM. / 

 PROFUNDUS . - 



EXT. CARPI 

 ^r-'rPAOIALlS. 

 £^lA-BRACHiORADIAL 

 iilLJ-RADIUS. 



SUBLIMIS 



FOREARM 



pronator teres .>^;^;,^ 

 Vlex carpi RADIALIS 

 palmaris udngus. tibialis anterior 

 iflexor digitorum ext. digitorum long 



peroneus longus 



SOLEUS. 

 FIBULA. 



GRACILIS. 



, ADDUCTOR MAGNUS. 



SEMIMEMBRANOSUS. 



SEM TENDINOSUS. 



HUMERUS' 

 C. UPPER ARM 



Fig. 235. — Muscles of arm and leg in cross section. A, cross section of forearm; 

 B, cross section of lower leg; C, cross section of upper arm; D, cross section of thigh. 

 (Redrawn after Braus.) 



which flexes the wrist and pronates the forearm. On the medial side 

 of the arm, the two groups are separated by the ulna bone. 



Among the extensor muscles of the forearm are the extensor carpi 

 radialis longus, and the extensor carpi radialis brevis, which lie on the 

 radial side, the extensor carpi ulnaris of the ulnar side, and intermediate 

 between these, the extensor digitorum communis and extensor digiti 

 quinti proprius. Deeper muscles beneath these include the supinator, 

 abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, 

 and extensor indicis proprius. 



Included in the flexor-pronator group of muscles are the pronator 

 teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor 

 digitorum sublimis, flexor digitorum profundus, flexor pollicis longus, and 



