THE ANTERIOR LIMB 269 



6. Muscles arising from the bones of the hand and inserted on the 

 individual digits. 



(a) The flexor digiti quinti. Origin: Pisiform bone and ten- 

 don sheath of the flexor digitorum profundus. Insertion: 

 Sesamoid bones of the metacarpophalangeal joint of the 

 fifth digit, extending to the ungual phalanx. This is a small 

 muscle superficial to the most lateral division of the tendon 

 of the flexor digitorum profundus. It represents both the 

 flexor digiti quinti brevis and the abductor digiti quinti of 

 some species. 



(b) The lumbricales. Three in number. Origin: From the 

 point of division of the tendon of the flexor digitorum pro- 

 fundus. Insertion : Medial side of the first phalanx in each 

 of the third, fourth, and fifth digits. 



(c) The adductor digiti quinti, adductor digiti quarti, and ad- 

 ductor indicis. Three slender muscles. Origin: Close 

 together on the dorsal part of the tendon sheath of the 

 flexor digitorum profundus. Insertion: By long thin ten- 

 dons, respectively, to the radial sides of the fifth and fourth 

 digits and the ulnar side of the second digit, just dorsal to 

 the interossei. 



(d) The flexor poUicis brevis. A minute muscle. Origin: The 

 lateral part of the transverse carpal ligament. Insertion: 

 The outer side of the base of the first phalanx of the pollex. 



(e) The interossei. Origin: In pairs from the bases of the 

 second to fifth metacarpals and related portions of the 

 carpal bones. Insertion : Sesamoid bones of the metacarpo- 

 phalangeal joints. The fibres of each pair interlace so that 

 the members cannot be smoothly separated. Differentia- 

 tion into volar and dorsal interossei is suggested, but they 

 cannot be dissected apart. 



Blood-Vessels and Nerves of the Arm and Forearm 



The axillary artery gives rise to posterior and often anterior 



branches before turning into the arm as the brachial artery. The 



anterior and posterior circumflex arteries to the neck of the humerus 



and adjacent muscles may arise as one or several branches, of which 



