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Show 700 MR. T. M A N N E R S - S M I T H O N T H E [Dec. 4, tendon and from the sesamoid bones in the tendon. They terminate in very slender tendons, which, after resting upon the corresponding tendon of sublimis, spread out into a thin fascia which blends with the digital sheaths of the profundus. The first, third, and fourth are larger than the second, which is very small. The first is more probably an abductor than a flexor of the pollex. The others give off two slender fascial slips, one on each side of the profundus tendon, to first phalanx, and send a third slip forwards to blend with the digital sheaths of the tendons of profundus. This muscle is not mentioned by Owen. Mivart says that flexor brevis is most probably absent in Echidna and Ornithorhynchus. Whilst the origin of a sublimis from the tendon of a profundus is common in Amphibians, it is rare amongst Mammals. Flexor carpi radialis is a large muscle. It arises from the lower end of the internal condyle, and is inserted below into a fairly large radial sesamoid bone. From the sesamoid bone slips pass on the radial side to the scapho-lunar and trapezium ; on the uluar side to pisiform and, downwards, to second metacarpal. The muscle is supplied by the median nerve. In Echidna this muscle passes to metacarpal bones of pollex and index. Pronator radii teres.-Arises from the inner condyle of humerus. It is inserted into middle of radius, a little below and on the opposite surface to supinator brevis. Flexor carpi ulnaris is a large flat muscle, arising by two heads from the internal condyle of the humerus : from the posterior border of the ulna and expanded upper extremity of olecranon. The tendon is inserted into the pisiform, and sends slips to the fourth and fifth metacarpals. This muscle is supplied by the ulnar nerve. Supinator brevis.-This is a somewhat triangular muscle. It arises from the external condyle, beneath the radial extensors of the wrist. It is inserted into the upper and middle fourths of the shaft of the radius. It is supplied by the posterior interosseous nerve. This muscle is not mentioned by Owen. Extensor carpi radialis longior.-Arises from the lower third of the supinator side of the shaft of the humerus. Below it divides into three tendons, Avhich pass to the bases of the second, third, and fourth metacarpal bones. Supinator longus.-Arises from the loAver end of the humerus, beneath the longior. It is inserted into the posterior surface of the peculiar large scapho-lunar. The muscle having this origin and insertion in Echidna is described by Mivart as the extensor carpi radialis longior. Only one radial extensor is described by Owen in Ornithorhynchus corresponding to longior. Supinator longus is not described by him. Extensor communis digitorum.-Arises by a common tendon from the external condyle. It expands on the back of the wrist, the expansion containing a fibro-cartilage. The expansion divides into two parts, each part giving off three tendons. Two go to the |