| OCR Text |
Show 774 MR. ST. GEORGE MIVART ON THE [Julie 27, lines results, four points being directed forwards and three backwards (fig. 4, I, 2, .*», 4). Of the four vertically superimposed cones of each vertebra, the topmost one, or the dorsal lateral cone (fig. 4, i), arises from the neural spine (N.) and the zygapophysis (z.). The cone next below, or the upper median lateral cone (fig. 4, 2), takes origin also from the zygapophysis; but below from the transverse process or (in more posterior caudal vertebrae) from the strong fascia which takes its place (t.). The next cone below, or the lower median lateral cone (fig. 4, 3), arises from the same transverse process or fascia and from the root of the inferior spinous process. The lowest, or ventral lateral cone (fig. 4, 4), springs from (h) the inferior spinous process itself. This arrangement continues forwards to about the fourteenth caudal vertebra. Then the bases of the cones become excluded from the articular processes and from the roots of the haemal spines by the intrusion and backward prolongation of a supracaudal muscular mass coming from the trunk (the sus-caudien externe of Meckel, vol. v. p. 284), and by that of the femoro-caudal below (fig. 5, S. C. and F. C.) ; so that the series of cones, being thus modified, come to form a muscular sheath for these intruding muscles, the sheath being strongly attached still to the ends of the transverse processes and of the neural and haemal spines. Fig. 5. Muscles of right half of a transverse vertical section of the tail at the seventh caudal verlebra, showing the separation of the caudal cones from the vertebra by the intrusion of the supracaudal above and of the femoro-caudal below. A. Superior lateral caudal cones. B. Inferior lateral caudal cones. F. C. Femoro-caudal. S. C. Supracaudal. The two series of median lateral cones more and more approximate as they approach the trunk, and, ultimately coalescing, are inserted strongly into the first caudal transverse process (fig. 15, a?). The dorsal lateral cones, much modified, continue on as the longissimus dorsi. The ventral lateral cones terminate mainly by a very strong tendon implanted into the posterior end of the tuberosity of the ischium (close to the origins of the two parts of the semimembranosus), a portion, however, running on into a sphincter cloacee*. Of the intruding muscular masses the femoro-caudal, inserted into the femur, extends for about one-sixth of the length of the tail, as Meckel saysf, or to about the thirteenth caudal vertebra. * Meckel, loc. cit. p. 285. t Loc. cit. p. 286. |
