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Show 170 DR. R. W. SHUFELDT ON [Apr. 1, in each case into the base of the second, third, and fourth metacarpal bones. Just beyond its origin this muscle is very thick and fleshy, and in this locality fuses to some little extent with the supinator longus, while at its insertion a thin tendinous expansion more or less unites its slips of division, and spreads out over the back of the carpus. 38. Extensor carpi radialis.-Running parallel with the extensor digitorum longus, this muscle likewise arises, tendinous, from the external condyle of the humerus, and, as it approaches the carpus, it forms a slender tendon which inserts itself into the os carpi radiale. This muscle has not more than a quarter the bulk of the extensor digitorum longus, with which it is quite intimately connected along its radial border. 39. Extensor digitorum brevis.-Superficially, on the back of the manus, we observe a divided set of muscles, which constitute the short extensors of the phalanges. Five-parted, but each slip more or less distinct, the extensor digitorum brevis arises from the dorsal aspect of the five metacarpal bones at their proximal extremities, and from the ossicles of the first row of the carpus. These slips are fleshy over the back of the hand, but become tendinous, each one at the bases of the digits, and a tendon runs along the back of each phalanx to the base of the ungual joint, where it is, in each case, inserted. Proximally, these muscular slips are imbricated, while distally their tendons, as they pass over each phalangeal joint in the fingers, send down lateral tendinous slips on either side, which attach to the sides of the heads of the finger-bones. 40. Extensor carpi ulnaris.-Springing from the postero-external aspect of the external condyle of the humerus, in common with the flexor carpi ulnaris, by a strong tendon, this muscle passes down the side of the forearm ; when opposite the radial side of the wrist it develops a strong tendon which, passing between the muscles of the hand on that side, finally inserts itself into the proximal end of the fifth metacarpal, upon its external surface. 41. Ulno-metacarpalis pollicis.-I propose this name for the present muscle in lieu of the " Ulno-pollicialis dorsalis s. Abductor pollicis longus " of Fiirbringer, or even the " M. ulno-metacarpialis /" of Hoffmann. It is the Abductor pollicis longus of Stannius, the Extensor ossis metacarpi pollicis of Mivart and Sanders. It arises from the dorsal aspect of the lower third of the forearm ; springing from the upper surface of the shaft of the ulna, it passes obliquely across the carpus, to finally develop a strong little tendon which is inserted into the proximal end of the pollex metacarpal, upon its dorsal side. 42. The flexor carpi ulnaris arises by two heads-one from the posterior surface of the radial condyle of the humerus, and the other from the side of the proximal extremity of the ulna and from the olecranon process of that bone. These are at first strong tendons, but soon become carneous and forming a flat, powerful muscle running down the outer side of the forearm, which again becomes tendinous at the wrist, to finally insert itself into the pisiform bone, upon the |