422 A MANUAL OF ANATOMY 



is to be noted. The posterior interosseous artery will be found to give of 

 its posterior interosseous recurrent branch as soon as it reaches the back o 

 the forearm. This branch is to be followed upwards beneath the anconeu! 

 to the back of the external epicondyle, where it anastomoses with the posterio: 

 terminal branch of the superior profunda. If well injected, it will be founc 

 to give branches to the back of the olecranon process, which anastomose 

 with branches of the posterior ulnar recurrent to form the olecranon rete 

 The posterior interosseous artery, as it descends with the nerve, gets verj 

 small, and usually ceases before reaching the wrist, where its place is taker 

 by the posterior branch of the anterior interosseous, with which it anas 

 tomoses. 



The muscles of the deep layer are then to be dissected in the following order 

 supinator radii brevis, extensor ossis metacarpi pollicis, extensor brevii 

 poUicis, extensor longus pollicis, and extensor indicis. The posterior annula: 

 ligament is next to be carefully dissected, and, by opening it up, the fibro 

 osseous canals which it forms with the grooves on the lower ends of the radiu; 

 and ulna are to be studied. The localization of the various tendons in thes( 

 canals is to be mastered, and careful attention is to be given to their synovia! 

 sheaths. The mode of termination of the posterior interosseous nerve is alsc 

 to be shown at this stage. It will be found to end beneath the tendons o: 

 the extensor communis digitorum in a gangliform enlargement, from whicl 

 articular twigs are given ofE to the adjacent joints. The radial artery or 

 the back of the wrist and its branches are next to be dissected, and th( 

 dissector is to note that the artery, just before it dips between the two heads 

 of the abductor indicis, is crossed by the tendon of the extensor longus pollicis 

 In connection with the posterior radial carpal artery, the posterior ulnar carpa' 

 is to be shown, as well as the posterior carpal arch, beneath the extensoi 

 tendons. The inner two dorsal interosseous arteries are to be shown arising 

 from this arch, and they are to be followed downwards over the inner twc 

 interosseous spaces to near the clefts between the middle and ring, and ring 

 and little fingers, where each divides into two dorsal collateral digital branches 

 The inner of the two arteries may give a branch to the inner side of the little 

 finger, or this may arise from the posterior ulnar carpal. The first dorsal 

 interosseous artery is to be followed from the radial over the second inter- 

 osseous space to near the cleft between the index and middle fingers, where it 

 also divides into two dorsal collateral digital arteries. The superior perforating 

 branches of the deep palmar arch are to be shown after they have pierced the 

 upper ends of the inner three interosseous spaces between the two heads oi 

 the dorsal interosseous muscles, where each joins a dorsal interosseous artery. 

 Each of these dorsal interosseous arteries may give off an inferior perforating 

 branch, before it bifurcates, to join a digital artery from the superficial palmar 

 arch. The arteria dorsalis pollicis is next to be shown, and it will be found to 

 divide into two branches (which sometimes arise separately) for the sides of the 

 thumb. Lastly, the arteria dorsalis indicis, which arises from the radial just 

 before it leaves the back of the wrist, is to be followed along the outer side 

 of the second metacarpal bone to the outer side of the index finger. 



The interosseous muscles are next to be dissected. In cleaning the palmar 

 interossei the interosseous fascia is to be noted, and its relation to the central 

 division of the palmar fascia is to be revised. In cleaning the dorsal inter- 

 ossei a thin, deep dorsal fascia will be removed. It will also be necessary tc 

 dissect the transverse metacarpal (deep transverse) ligament, which stretches 

 across the heads of the four inner metacarpal bones on their palmar aspects. 

 This having been cut, the muscles are now to be fully dissected, and theii 

 nerve-supply and actions carefully studied. 



Elbow- Joint. — The muscles related to this joint are to be replaced, and theiii 

 relation to it noted. The adjacent nerves are also to be observed, and th«! 

 anastomoses of arteries around the joint are to be thoroughly mastered. Thti 

 ligaments which compose the capsule, namely, anterior, posterior, externa)! 

 lateral, and internal lateral, are to be dissected, and the joint is then to be| 

 opened. The articular surfaces are to be examined, the pads of fat noted) 

 and the synovial membrane and movements studied. \ 



