THE INTEROSSEOUS MUSCLES. Si 



adductor obliquus and the flexor brevis pollicis, where it divides artery of 

 into the two collateral branches of the thumb ; these are distributed the tnum b ; 

 like the arteries of the superficial arch (p. 72). 



e. The radial digital branch of the index finger (d) (arteria artery of 

 radialis indicis) is directed over the first dorsal interosseous 

 muscle (j), and beneath the adductors of the thumb, to the radial 

 side of the forefinger. At the lower border of the adductor 

 trans versus (D), this branch is usually connected by an offset 

 with the superficial palmar arch ; and at the end of the digit it 

 unites with the branch furnished to the opposite side by the uliiar 

 artery. 



The DEEP PART OF THE ULNAR NERVE ( 2 ) accompanies the deep Deep branch 

 arterial arch as far as the muscles of the thumb, where it terminates 

 in offsets to the two adductors. 



Branches. Near its origin the nerve furnishes branches to the muscular 

 muscles of the little finger. In the palm it gives offsets to all the offsets - 

 palmar and dorsal interosseous muscles, and to the inner two 

 lumbrical muscles ( 3 ), besides the terminal branches before men- 

 tioned. 



The TRANSVERSE METACARPAL LIGAMENT is formed by crOSS fibres TransA-erse 



uniting the palmar ligaments of the metacarpo-phalangeal articula- 

 tions of the fingers, and serves to bind together the heads of the 

 inner four metacarpal bones. To its upper border the fascia cover- 

 ing the interosseous muscles is attached. The ligament should now 

 lie taken away to see the interosseous muscles. 



The INTEROSSEOUS MUSCLES, so named from their position Seven inter- 

 between the metacarpal bones, are seven in number. Two muscles muscles 

 occupy each space, except the first, where there is only one. They 

 arise from the metacarpal bones, and are inserted into the first 

 phalanges of the fingers and the expanded extensor tendons. They divided into 

 are divided into palmar and dorsal ; but all are seen in the palm of JJonSif and 

 the hand, though the former project more than the others. 



The palmar muscles (fig. 33), three in number, are smaller than Palmar go 



" . , .... .1 i , to index, 



the dorsal, and have each a single origin ironi the side of the ring, and 



metacarpal bone of the finger to which it belongs. The first is 

 placed on the ulnar side of the index finger, the second and third 

 on the radial side of the ring and little fingers respectively. 



The dorsal muscles (fig. 34), one in each space, arise by two Dorsal : two 

 heads from the lateral surfaces of the metacarpal bones between fJ^J?^J e 

 which they lie. The first (abductor indicis) is inserted on the each to 

 radial side of the index finger, the second on the radial and the rmg^ingers. 

 third on the ulnar side of the middle finger, and the fourth on the 

 ulnar side of the ring finger. 



Both sets of muscles have a similar termination (fig. 29, Common 

 p. 75) : the fibres end in a tendon, which is inserted into the side 

 of the first or metacarpal phalanx, and sends an expansion to join 

 the extensor tendon on the dorsum of the bone. 



Action. They bend the metacarpo-phalangeal joints by their Action as 

 attachment to the first phalanx, and extend the two interphalangeal extensors, 

 joints through their union with the extensor tendon. 



D.A. G 



