THE VESSELS. 319 



Position : covered by pronator teres, flex, sublim., palmar long., flex. carp, 

 ulnar., passing before N.ulnaris. Branches: a. an anterior between pronat or 

 teres and brachialis internus ; b. to N. ulnaris above. 



2. Interossea. Origin : from the ulnaris behind, close under the last. 

 Course : directly backwards and downwards, to the centre of the fore-arm ; 

 it bifurcates into : 



a. Interossea anterior (s. interna). Origin : above lig. interosseum. Course : 

 on the anterior surface of lig. interosseum, bet-ween flex, digit. profund. (in- 

 side), polite, longus" (outside), perforates under pron. quadrat, the lig. in- 

 teross., and passes upon the dorsal surface of the carpus into the rete dor- 

 sale. Branches : several artt. perforantes pass through lig. inteross. back- 

 wards to the deep muscles ; an anterior superior branch accompanies the 

 nerv. medianus as far as the hand ; an inferior passes behind pronat qua- 

 dratus downwards to the rete carpi volare. 



b. Interossea posterior (s. externa) ; smaller than the last ; passes through 

 two inches below the articulation between ulna and radius upon the 

 dorsal region of the fore-arm, and divides immediately into : 



1. Interossea recurrens (s. radial, poster.') ; ascends on the radial side 

 of the ulna, covered by anconeus parvus, to the rete cubitale. 



2. Interossea descendens, descends, nearer to the ulna, upon the dorsal 

 side of lig. inteross. as far as the carpus. Branches to extens. com- 

 mun. digit. 5, carp, ulnaris and skin. 



3. Art. nutritia ulnaris, a small branch, about the middle of the art. ulnaris, 

 passes through a /cram, nutritium in the ulna [from below upwards] ; some- 

 times also a branch to the radius (or even from the anterior circumference of 

 interossea anterior). 



4. Ramus dorsalis, terminal branch of ulnaris, passes under the tendon of 

 m. flex, carpi ulnaris to the back of the carpus into the rete carpi dorsale ; 

 giving off in its passage the dorsal, ulnar. to the little finger. 



5. Ramus volaris, terminal branch of the ulnaris, passes close to os pisi- 

 forme, and above os hamatum (hamulus) and lig. carp, propr., covered by 

 aponeurosis palmar, and m. palmar, brevis, into the hollow of the hand, gives 

 branches to the muscles of the ball of the little finger, and 



a. Ram. sublimis, which externally passes into arc. volaris sublimis ; and, 



b. Ram. profundus, which gives off an internal branch for the volar surface 

 of the little finger, and under the tendons of mm. flexor, digit, goes to form 

 arc. volar. profund. 



569. The vascular arches of the hand. 



1. Arcus (8. rete) carpi dorsalis, is situated upon the dorsal surface of the 

 metatarsus, covered by lig. carpi dorsale, and the tendons of the extensor 

 muscles ; is formed by ram. transfers, of art. radialis and ulnaris ; gives off: 



a, Rami ascend entes, which pass opposite to branches of art. inteross. anter. 



b. Rami descendentes , the short roots, anastomosing with artt. perforantt. 

 arcus volaris profundi of 



