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Show 178 DR. R. W. SHUFELDT ON [Apr. 1, the mesially situated spinalis dorsi, and the sacro-lumbalis upon outer side. And its origin seems to be in the sacro-lumbar region, where it arises, for the most part, from the diapophyses of the vertebrae ; but as it passes to the middle of the back, and the cervical region beyond, its attachment becomes insertional, and by tendinous points of development it makes fast to the apices of the postzyga-pophyses, and to the dorsal surfaces of the ribs on their outer sides. Origin and insertion apparently are more or less blended in mid-dorsal region, but this muscle is distinctly insertional in the cervico-dorsal and cervical regions, while still more anteriorly the longissimus dorsi becomes specialized and goes to form muscles that will next be described. 58. Complexus.-This is a most powerful muscle here, constituting as it does the antero-median insertion of the longissimus dorsi upon the skull. W e may consider it as coming off from more or fewer of the post-axial vertebrae, and it is inserted into the posterior border of the parietal bone, as well as into the hinder surface of the cranium below it. All these muscles of the neck are quite intimately blended, more especially the two or three at present under consideration. 59. The Trachelo-mastoid is another muscle which continues the longissimus dorsi forwards to the skull behind, being situated external to the last, and inserted principally into the os occipitale externus. 60. Transversalis colli is the last of the three muscular fasciculi which insert themselves into the posterior aspect of the cranium, as the forward prolongations of the longissimus dorsi. It attaches itself at a point lower than any of them, being inserted into the basioccipital near the rectus anticus major, and intimately associated on its outer side with the cervicalis ascendens. This muscle is the complexus minor of Mivart, as found by him in Parson's Chameleon. 61. Sacro-lumbalis.-In our present subject this muscle arises from the superficial aspect of the hinder end of the ilium of the corresponding side, and, passing as a narrow band over the pelvic region, it commences to broaden as it covers the ribs. From thence on to the neck it has a width greater than the spinalis dorsi and the longissimus dorsi together, but mesiad it is not so thick vertically, while it gradually becomes thinner as it passes outwards. As in the case of the two muscles just mentioned, the general direction of its fibres is directly forwards, and its insertion is found to be upon the dorsal surface of each rib, for more or less their inner thirds. These insertions are tendinous and very firm, while the ventral surface of the muscle itself is quite intimately blended with the intercostals, and more posteriorly with the quadratus lumborum. On its inner side, for its entire length, it is easily dissected from the longissimus dorsi, the two muscles being quite distinct, while anteriorly it merges into the cervicalis ascendens, a muscle which constitutes its proper continuation forwards. 62. Cervicalis ascendens.-This muscle is handsomely developed |
