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Show 1867.] MYOLOGY OF IGUANA TUBERCULATA. 783 appear to go mainly to the ulna. Thus its insertion has much resemblance to that of the same muscle in the Echidna. The brachialis anticus (figs. 1, 2, 6, 8 & 10, B. A.), which may be, as Meckel appears to think*, a humeral head of the biceps, springs from the front of the shaft of the humerus, immediately below the insertions of the deltoid, epicoraco-humeral, and pectoralis major. It soon fuses with the biceps, and is inserted in common with it into the upper ends of the flexor surfaces of both radius and ulna. The fibres of this muscle, however, appear to be connected mainly, if not exclusively, with the radius. Supinator longus. This muscle (figs. 1, 6, 10 & 11) is exceedingly large, and, as Meckel observesf, arises by two heads, which do not unite till far down the forearm (fig. 1, S. Li). Indeed I find that that head which has the more posterior (lower) origin may be again divisible at and near its origin into two portions, of which the anterior (upper) one is much the smaller; all these parts, however, arise from the external condyle, and have a common insertion into the radial margin of the radius for almost its whole length, and therefore side by side with the pronator teres as far as the latter extends. The head, which has the more posterior (lower) origin, is intimately connected with the radial extensor. The extensor carpi radialis, which appears to answer to both the longior and brevior of mammals, arises by tendinous fibres from the outer and posterior surface of the external condyle, immediately superficial to the posterior (lower) part of the origin of the supinator longus, with which, for some distance, it is very intimately connected. Passing downwards (fig. 1, E.Ri) it divides into three parts, which are inserted, each by a tendon, into the proximal ends of the dorsal surfaces of the second, third, and fourth metacarpals. Extensor communis digitorum. As Meckel observes %, this muscle has, as it were, " descendu a la main" (fig. 11, E. Ci). It is small, arises from the carpus, and is inserted into the bases of the digits. lt is much subdivided, there being more or less distinct fleshy bundles for the several digits. The extensor carpi ulnaris (fig. 1, E. U., and fig. 11, E. C. U.) is rather indistinct. It arises indeed by tendinous fibres from the posterior surface of the external condyle; but its insertion is into the adjacent border of another muscle, the flexor carpi ulnaris. Extensor ossis metacarpi poliicis. This is a rather thick muscle which arises from the posterior surface of rather less than the distal half of the ulna. It is inserted into the metacarpal of the pollex (fig. 1\,E.M.P.). Pronator teres (figs. 6 & 12, P. Ti). The origin of this muscle is by a very strong tendon attached to the summit of the internal condyle. Its fibres spread out, and are inserted into the lower two-thirds of the radial margin of the radius. The flexor carpi radialis (figs. 6, 9, F. R., and fig. 12, F. C. R.) arises from the internal condyle immediately below the origin of the * Loc. cit. p. 362. f Loc. cit. p. 367. | Loc. cit. p. 391. |
