THE MUSCLES AND FASCIA OF THE LOWER EXTREMITY 465 



and third are inserted into the middle finger, the former into its radial, the latter 

 into its ulnar side. The fourth is inserted into the ulnar side of the ring finger. 



The Interossei volares (Palmar inter ossei), three in number, are smaller than the 

 Interossei dorsales, and placed upon the volar surfaces of the metacarpal bones, 

 rather than between them. Each arises from the entire length of the metacarpal 

 bone of one finger, and is inserted into the side of the base of the first phalanx and 

 aponeurotic expansion of the Extensor communis tendon to the same finger. 



The first arises from the ulnar side of the second metacarpal bone, and is inserted 

 into the same side of the first phalanx of the index finger. The second arises from 

 the radial side of the fourth metacarpal bone, and is inserted into the same side 

 of the ring finger. The third, arises from the radial side of the fifth metacarpal 

 bone, and is inserted into the same side of the little finger. From this account 

 it may be seen that each finger is provided with two Interossei, with the exception 

 of the little finger, in which the Abductor takes the place of one of the pair. 



As already mentioned (p. 461), the medial head of the Flexor pollicis brevis is 

 sometimes described as the Interosseus volaris primus. 



FIG. 428. The Interossei dorsales of left hand. 



FIG. 429. The Interossei volares of left hand. 



Nerves. The two lateral Lumbricales are supplied by the sixth and seventh cervical nerves, 

 through the third and fourth digital branches of the median nerve; the two medial Lumbricales 

 and all the Interossei are supplied by the eighth cervical nerve, through the deep palmar branch 

 of the ulnar nerve. The third Lumbricalis frequently receives a twig from the median. 



Actions. The Interossei volares adduct the ringers to an imaginary line drawn longitudinally 

 through the center of the middle finger; and the Interossei dorsales abduct the fingers from that 

 line. In addition to this the Interossei, in conjunction with the Lumbricales, flex the first 

 phalanges at the metacarpophalangeal joints, and extend the second and third phalanges in 

 consequence of their insertions into the expansions of the Extensor tendons. The Extensor 

 digitorum communis is believed to act almost entirely on the first phalanges. 



THE MUSCLES AND FASCLffi OF THE LOWER EXTREMITY. 



The muscles of the lower extremity are subdivided into groups corresponding 

 with the different regions of the limb. 



30 



I. Muscles of the Iliac Region. 

 II. Muscles of the Thigh. 



III. Muscles of the Leg. 



IV. Muscles of the Foot. 



