THE UPPER LIMB 421 



the flexor brevis pollicis. the others being supplied by the deep division of the 

 ulnar nerve. The three hypothenar muscles are then to be dissected. The 

 profunda branch of the ulnar artery and deep division of the ulnar nerve pass 

 between the abductor, and flexor brevis, minimi digiti, and then pierce the 

 opponens minimi digiti, these three muscles being suppUed by the deep division 

 of the nerve. 



The anterior annular Ugament is now to be dissected, the structures related 

 tc it superficially are to be revised, and the ligament is then to be divided 

 in order to examine the contents of the fibro-osseous canal which it forms 

 with the front of the carpus. The great palmar bursa is to be carefully 

 noted passing upwcirds beneath it, and descending will be found the super- 

 ficial and deep flexor tendons, tendon of the flexor longus pollicis, and 

 median nerve. Lying in a special compartment of the Ugament, at its outer 

 part, will be found the tendon of the flexor carpi radialis, as it traverses the 

 groove on the palmar aspect of the trapezium. The superficial flexor 

 tendons may then be divided in the palm, to enable the deep flexor tendons 

 to be raised and placed over the handle of a scalpeL The lumbricales, 

 arising from these deep tendons, are then to be dissected, and their ner\'e- 

 supply noted, namely, the deep division of the ulnar for the inner two, and the 

 median for the outer two. The deep flexor tendons are to be cut and turned 

 downwards with the lumbricales, in order to expose the radial artery in the 

 palm, where it forms the deep palmar arch, wiiich is completed by the profunda 

 branch of the ulnar. The arteria princeps poUicis and arteria radiahs indicis 

 are to be shown cirising from the radial as it passes to the front of the hand, 

 and the palmar interosseous, recurrent, and superior perforating branches of 

 the deep palmar arch are to be dissected. The deep division of the ulnar 

 nerve is next to be followed out, and its extensive muscular distribution is to 

 be carefully studied. 



Baek of the Forearm and Hand. — The skin having been carefully removed, 

 the dorsal venous arch, with its tributaries, is to be shown on the back of the 

 hand, and the radial nerve and the dorsal branch of the ulnar nerve are to be 

 followed to their digital distributions. In removing the deep fascia from the 

 back of the forearm, care should be taken to leave intact the thickened 

 portion of it on the back of the wrist which forms the posterior annular liga- 

 ment. The muscles on the outer side of the forearm are to be dissected first, 

 in the follo\^nng order : brachio-radiaUs, extensor carpi radialis longior, 

 and extensor carpi radialis brevior. The superficial layer of muscles on 

 the back of the forearm are then to be dissected as follows : extensor com- 

 munis digitorum, extensor minimi digiti, extensor carpi ulnaris, and anconeus. 

 Without disturbing meanwhile the posterior annular ligament, the extensor 

 tendons are to be followed over the back of the hand to their insertions. In 

 doing this, the thin, deep fascia on the dorsum, continuous above with the 

 posterior annular ligament, is to be noted, and care is to be taken to preserve 

 the dorsal arteries. The dissector will find the tendon of the extensor indicis 

 lying inside the common extensor tendon to the index finger, and the tendon 

 of the extensor minimi digiti will usually be found to be double. The flat 

 bands which connect the ring-finger tendon with that on either side of it 

 are to be showTi, as well as a band connecting the middle-finger tendon 

 with the common extensor tendon to the index finger. The expansions of 

 the common extensor tendons over the backs of the first phalanges are 

 to be shown, and it will be seen that these receive the insertions of the 

 lumbricales and interossei. The mode of insertion of the extensor tendons 

 is then to be examined. 



Returning to the back of the forearm, the superficial muscles are to be held 

 well aside, and the posterior interosseous nerve and artery dissected. The 

 nerve, having wound round the outer side of the radius in the supinator 

 radii brevis, will be found emerging from that muscle behind near its lower 

 border, and a little below this the artery meets it, after having passed back- 

 wards between the radius and ulna. The nerve is now to be followed down- 

 wards between the superficial and deep muscles, and then beneath the extensor 

 longus pollicis, but no lower in the meantime, and its muscular distribution 



