INTEROSSEAL MUSCLES. 221 



their insertion, with the tendons of the interossei and metacarpo- 

 phalangeal articulations. 



The Palmar interossei, three in number, are placed upon the meta- 

 carpal bones, rather than between them. They arise from the base 

 of the metacarpal bone of one finger, and are inserted into the base 

 of the first phalanx and aponeurotic expansion of the extensor tendon 

 of the same finger. The first belongs to the index finger; the second, 

 to the ring finger ; and the third, to the little finger ; the middle 

 finger being excluded. 



Relations. -By their palmar surface with the flexor tendons and 

 with the deep muscles in the palm of the hand. By their dorsal 

 surface with the dorsal interossei. On one side with the metacarpal 

 bone, on the other with the corresponding dorsal interosseous. 



On turning to the dorsum of the hand, the four dorsal interossei 

 are seen in the four spaces between the metacarpal bones. They are 

 bipenniform muscles, and arise by two heads, from the adjoining 

 sides of the base of the metacarpal bones. They are inserted into 

 the base of the first phalanges, and aponeurosis of the extensor ten- 

 dons. 



The first is inserted into the index finger, and from its use is called 

 abductor indicis ; the second and .third are inserted into the middle 

 finger, compensating its exclusion from the palmar group ; the fourth 

 is attached to the ring finger ; so that each finger is provided with 

 two interossei, with the exception of the little finger, as may be 

 shown by the adjoining table : 



one dorsal (abductor indicis), 

 one palmar. 

 Middle finger, two dorsal. 



n . ( one dorsal, 

 Ring finger j one p a j mai , 



Little finger, remaining palmar. 



Relations. By their dorsal surface with a thin aponeurosis which 

 separates them from the tendons on the dorsum of the hand. By 

 their palmar surface with the muscles and tendons in the palm of 

 the hand. By one side with the metacarpal bone; by the other 

 with the corresponding palmar interosseous. The abductor indicis 

 is in relation by its palmar surface, with the adductor pollicis, the 

 arteria magna pollicis being interposed. The radial artery passes 

 into the palm of the hand between the two heads of the first dorsal 

 interosseous muscle and the perforating branches of the deep palmar 

 arch, between the heads of the other dorsal interossei. 



Actions. The actions of the muscles of the hand are expressed 

 in their names. Those of the radial region belong to the thumb, 

 and provide for three of its movements, abduction, adduction, and 

 fiexion. The ulnar group, in like manner, is subservient to the same 

 motions of the little finger, and the interossei are abductors and 

 adductors of the several fingers. The lumbricales are accessory in 



