394 



A Manual of anatomy 



The palmar interossei belong to the index, ring, and Httle 

 fingers, and they are named from without inwards — first, second, 

 and third. Each is connected only with one metacarpal bone. 

 The first arises from the mner aspect of the shaft of the second 

 metacarpal bone, and the second and third from the outer aspects 

 of the shafts of the fourth and fifth metacarpals. The fi-rst is 

 inserted partly into the inner side of the base of the first phalanx 

 of the index finger, and partly into the- expansion of the extensor 

 tendon on the dorsal aspect of that phalanx. The second and 

 third are inserted in a similar manner in the case of the ring and 

 little fingers, except that each is inserted into the outer side of the 

 base of the first phalanx. 



The palmar interossei are covered by a thin fascia, called the 

 interosseous fascia. At either side it joins the thenar and hypo- 

 thenar portions of the palmar fascia, and interiorly it is connected 

 with the transverse metacarpal and anterior metacarpo-phalangeal 



ligaments. Two septa pass 

 between it and the central 

 portion of the palmar fascia. 

 The dorsal interossei, 

 which are four in number, 

 belong to the index, middle, 

 and ring fingers, the middle 

 finger having two. They are 

 named from without inwards — 

 first, second, third, and fourth, 

 the first being specially called 

 the abductor indicis. Each 

 muscle arises by two heads 

 from the contiguous sides of 

 the shafts of the metacarpal 

 bones between which it is 

 placed, and always more ex- 

 tensively from the bone belong- 

 ing to the finger upon which 

 the muscie acts. The fibres 

 of each muscle end upon a 

 tendon which is placed in the 

 centre, and this tendon is in- 

 serted partly into the side of 

 the base of the first phalanx of 

 a finger, and partly into the 

 expansion of the extensor 

 tendon on the back of that 

 phalanx. The first or abductor 

 indicis is of large size. Its outer large head arises from the 

 proximal half of the inner margin of the first metacarpal bone, 

 and its inner small head from the whole length of the outer 

 aspect of the shaft of the second metacarpal. It is inserted 



Fig. 211.— The Dorsal Interosseous 

 Muscles of the Right Hand. 



