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Show 870 MR. ST. GEORGE MIVART ON THE [Dec. 6, the pronator quadratus), and into the radial carpal ossicle, into which are especially inserted the fibres from the interosseous ligament. Pronator quadratus* (figs. 12 & 15, P. Q). This is small, and confined to the lower part of the forearm. It springs from the radial aspect of the ulna and from the lower part of its flexor surface, with the pronator accessorius superficial to it on the flexor aspect of the arm. It is inserted into the flexor aspect of the radius for about its distal fourth, but it does not go to the radial ossicle. It is altogether a transverse layer running directly from the ulna to the radius. Flexor carpi ulnaris (figs. 1, 8, 10, & 11, F. U). This muscle is much more distinct from the flexor carpi radialis than it is in the Iguana, lt has a double origin-one from the internal condyle, the other (by a tendon common to it and the extensor carpi ulnaris) from the lower end of the back of the humerus. Passing downward, the two parts unite, but, before doing so, leave exposed one part of the flexor profundus digitorum, as another part of that muscle comes to the surface between the flexor ulnaris and flexor radialis. It is inserted into the palmar ossicle, and therefore superficially to the tendon of the extensor carpi ulnaris. Fig. 14. Deeper flexor sm-face of right forearm. F. D. Flexor profundus digitorum. F. P. Flexor longus poliicis. F. R. Flexor radialis. P. A. Pronator accessorius. P. T. Pronator quadratus. Flexor longus poliicis (figs. 8, 10, & 28, F. P). This large muscle has three distinct origins. The first is from the internal condyle, between the two tendons of origin of the flexor carpi radialis. The second is from the internal condyle, below the first head of origin. These two parts soon unite to form one belly. The third head of origin springs from the olecranon and the radial aspect of the upper part of the ulna. It unites with the other belly about the middle of the forearm (where the ulnar nerve comes out over it), and passing distad ends in a strong tendon which divides into four, one division going to each of the three radial digits (pollex, index, and mid digit), and the fourth division uniting with that tendon of the flexor profundus digitorum which goes to the fourth digit. * Meckel, /. c. p. 360. |
