OCR Text |
Show 1867.] MYOLOGY OF IGUANA TUBERCULATA. 785 Supinator accessorius (fig. 12, S. A.). Another muscle, which I also provisionally distinguish by a new name, arises from the internal condyle immediately below, but somewhat superficial to the pronator accessorius. It expands as it descends, and is inserted into about the proximal half of the ulnar margin of the ulna. The pronator quadratus (figs. 11 & 12, P. Qi) is broadest below, and becomes very narrow towards its upper end. It arises from the flexor surface of the distal half of the ulna and from the whole radial margin of that bone, and it is inserted into the flexor surface of the radius. Flexor carpi ulnaris (figs. 1, 6 & 9, F. U., and fig. 12, F. C Ui). This forms a large muscular sheet, which, as usual, has the ulnar nerve passing between its double origin-that from the internal condyle and that from the olecranon. It is inserted into both the pisiforme and fifth metacarpal, as Meckel observes*. This muscle receives on its postero-external side the insertion of the extensor carpi ulnaris, the two together forming a layer of muscle which wraps round the ulnar side of the forearm. The flexor sublimis digitorum (fig. 6, F. S. Di) is a thin muscle entirely confined to the handf- It arises from the annular ligament, and is inserted into the second phalanges of the digits, being perforated in each case by a tendon of the flexor profundus digitorum. Flexor profundus digitorum (figs. 6 & 12, F. P. D.). This is a very thick muscle, and has four, more or less distinct heads of origin. The first head arises from the internal condyle, immediately beneath the origin of the flexor carpi radialis; it very soon unites with the portion arising from the ulna (fig. 6, F.P.D. 1). The second head also springs from the internal condyle, just below the first head ; it also joins the portion arising from the ulna (fig. 6, F. P. D. 2). The third portion takes origin from the greater part of the flexor surface of the ulna. These three portions unite and give rise to a very strong tendon (in which is a palmar ossicle) ; and into the deep surface of this tendon are inserted muscular fibres, which spring from the carpus and constitute the fourth head of the muscle. From the distal margin of this tendon proceed the five perforating tendons, one going to each digit. Lumbricales. I have only observed six lumbrical muscles :- One going from the ulnar side of the index tendon to the ulnar side of the second digit. Two from the tendon of the third digit (one on each side), inserted into each side of the third digit. Two from the tendon of the fourth digit (one on each side), inserted into each side of the fourth digit. One from the radial side of the fifth digit, inserted into the radial side of the same digit. Lnterossei. There are dorsal interossei which arise from the carpus, and are inserted one on each side of the proximal phalanx of * Loc. cit. p. 383. t Meckel, loc. cit. p. 392. |