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Show 1867.] MYOLOGY OF IGUANA TUBERCULATA. 781 from the tendon of the latissimus dorsi. Is this head the homologue of the dorso-epitrochlear, which sometimes, as in Hyrax*, takes origin from the scapular arch, but normally springs from the tendon of the latissimus dorsi ? (3) The third, or external humeral head, arises from the whole outer surface of the humerus below the head of the hone, extending as it does above the insertions of the deltoid and infraspinatus (figs. 1, 2, 8 & 10, 77.3). (4) The last, or internal humeral head (figs. 6, 9 & 10, T. 4), similarly arises from the internal surface of the humerus to the head of the bone. At its summit this part of the muscle has contiguous to it, antero-internally, the short part of the coraco-brachialis and the insertion of the subscapularis, while the tendons of the latissimus dorsi and infraspinatus are contiguous to it on its posteroexternal side (fig. 9). Muscles of inside of right arm, the scapular arch being detached, and the costo-coracoid muscle (67. C.) being cut short and reflected. B. Biceps muscle. 67. Sternal margin of coracoid bone. C.B.I. First, or short, part of coraco-brachialis muscle. C. B. 2. Second, or long, part of coracobrachialis. C. C. Costo-coracoid. F. S. Flexor carpi radialis. F. U. Flexor carpi ulnaris. L. B. Latissimus dorsi. S. 2. Second part of subscapularis. 7.1. First, or external long, head of triceps. T.2. Second, or internal long, head of triceps. T. 4. Fourth, or internal humeral, head of triceps, t. Tendon from latissimus dorsi to triceps. All these four portions are united together at above the middle of the arm, and are together inserted into the proximal end of the ulna and into the patella-like sesamoid immediately above it. Coraco-brachialis. This muscle consists of two parts :- (1.) The first of these, or shorter portion, is a broad muscle, and much resembles the short coraco-brachialis of the Echidna f. It arises, by muscular fibres, from the whole outer surface of the coracoid, from the lower spur of the epicoracoid, and from the membrane * Proc. Zool. Soc. 1866, p. 340, fig. 5, B. e. t Trans. Linn. Soc. vol. xxv. p. 385. |
