OCR Text |
Show 1870.] MYOLOGY OF PLATYDACTYLUS JAPONICUS. 419 is inserted into the scaphoid bone of the carpus; it does not quite correspond to ext. carp, rad., but it does so more nearly than to any other extensor of the forearm. Extensor carpi ulnaris arises by two heads, one from the distal extremity of the outer condyle of the humerus, the other from the proximal half of the ulna; it is inserted into the pisiform bone and the base of metacarpal of the fifth digit. Extensor communis digitorum arises tendinous from the outer condyle between tbe last two muscles, and muscular from the whole length of the ulna, as far as its distal articulation; in the middle of the forearm it forms a thick fleshy mass, which soon divides into three broad tendons, which are inserted into the heads of the second, third, and fourth metacarpal bones; the one to the second sends a slip to be attached to the fascia covering the metacarpal bone of the pollex; in another specimen this part was divided into two, giving the appearance of five tendons instead of three. Interossei dorsales.-Each digit has two dorsal interossei, one on each side; they are inserted into the penultimate phalanx, being-united together on the dorsum by a raphe; this is a feature they all have in common. Their origins are as follows :-The one on the ulnar side of the fifth digit arises from metacarpal bone of the same ; that of the radial side from the tendon of the extensor digitorum, and also from the same metacarpal bone. The one on the ulnar side of the fourth digit arises from the same tendon with last, and also from its own metacarpal bone; the radial one of this digit from its own metacarpal bone. The one on the ulnar side of the third digit from the middle tendon of the extensor and its own metacarpal bone; the radial one of this digit from the ulnar side of the head of the metacarpal bone of the second digit. The ulnar of the second digit from its own metacarpal bone and extensor tendon; its radial from the metacarpal bone of pollex in conjunction with the single one belonging to the latter. Extensor ossis metacarpi poliicis arises from the distal end of the ulna for one-fourth of its length, and passing across tbe forearm it is inserted into the whole length of the radial side of the metacarpal bone of the pollex. Extensor brevis digitorum arises from the bone of the carpus representing the cuneiform, and immediately divides into five slips; the first passes across the hand to be inserted into the base of the first phalanx of the pollex; each of the other four slips ends in a slender tendon, which is inserted into the penultimate phalanx of each of the other digits. Complexus is the superficial muscle of the back of the neck. It is a distinct continuation forward of the longissimus and spinalis dorsi, and is inserted into the fascia covering the temporal muscle, into the supraoccipital and neural spine of the first vertebra, and also into the membrane which fills up the space between the parietal and the supra- and exoccipitals. Trachelo-mastoid is a continuation forward of the longissimus dorsi. It also arises from the zygapophysis of the first cervical |