OCR Text |
Show 1870.] MYOLOGY OF C H A M A E L E O N PARSONII. 887 Interossei. Those in the pes are substantially similar to those of the manus. APPENDICULAR NERVES. The brachial plexus. seems to be formed by three spinal nerves, and gives off the subscapular nerve from its posterior part. There is one great limb-nerve, which includes both the median and the ulnar nerves in it. The median. This great nerve perforates the coraco-brachialis (i. e. passes between the long and the short coraco-brachialis), and runs down between the postero-internal border of the brachialis anticus and the inner part of the triceps. At the bend of the elbow it perforates the pronator teres, and dipping down continues on between the last-named muscle and the flexor carpi radialis, the pronator accessorius, and the upper and larger condyloid belly of the flexor longus poliicis. The ulnar nerve accompanies the median till it has perforated the pronator teres, thus passing altogether in front of the elbow-joint. Then, leaving the median, it dips down between the pronator accessorius and the large inner condyloid head of the flexor longus poliicis. It continues along on the surface of the last-named muscle, and at the wrist is superficial to its tendon, but covered by the flexor ulnaris. It passes to the palm in the region of the fifth digit. The posterior interosseous nerve quits the median a little below the spot where the ulnar nerve leaves it. Passing down between the radius and tbe head of the pronator accessorius, it runs down the extensor surface of the arm upon the pronator quadratus, and covered by the extensor ossis metacarpi poliicis. It supplies the extensores metacarporum. The lumbar plexus is formed of two spinal nerves, as also is the sacral plexus. A short lumbo-sacral nerve connects the posterior root of the lumbar plexus with the anterior root of the sacral plexus. The anterior crural nerve is formed by the union of the two lumbar nerves, and descends in front of the anterior margin of the ilium at the outer border of the iliacus, which is supplied by a branch from it. The great sciatic nerve, formed by the union of the two sacral nerves, passes out very near to the anterior crural, being only separated from it by the breadth of the ilium. Covered by the ilio-peroneal, it passes down between the adductor and the biceps. A large branch is given off which is covered by the femoro-caudal, and passes round the head of the femur to near the origins of the semitendinosus and semimembranosus. The posterior tibial nerve, the continuation of the great sciatic, dips down between the peroneus and the flexor longus digitorum. It then crosses to the inner side of the leg beneath the gastrocnemius externus. PROC. ZOOL. Soc-!870, No. LIX. |