. The development of the chick; an introduction to embryology . »,-^*•c,-^ >p. S-li Fig. 234. — Frontal section including the same vertebral pri-mordia as Fig. 233, at a higher level through the neural arches,a. C, Anterior commissure of the spinal cord. v. R., Ven-tral root of spinal nerve. Other abbreviations as before (Fig;.232). It chondrifies separately from the vertebral body and in the case of the first vertebra it fuses subsequentlywith the remainder of the vertebral body, and disappears as THE SKELETOX 417 a separate component. Schauinsland has interpreted it as theh
. The development of the chick; an introduction to embryology . »,-^*•c,-^ >p. S-li Fig. 234. — Frontal section including the same vertebral pri-mordia as Fig. 233, at a higher level through the neural arches,a. C, Anterior commissure of the spinal cord. v. R., Ven-tral root of spinal nerve. Other abbreviations as before (Fig;.232). It chondrifies separately from the vertebral body and in the case of the first vertebra it fuses subsequentlywith the remainder of the vertebral body, and disappears as THE SKELETOX 417 a separate component. Schauinsland has interpreted it as thehomologue of the haemal arches of reptilia {, Sphenodon). The membrane represents not only the future bony partsbut the ligaments and periosteum as well. Hence we find thatthe successive membranous vertebrae are not separate structuresbut are united by membrane, , condensed mesenchyme, andare distinguishable from the future ligaments at first only bygreater condensation. In the stage of Fig. 233, chondrificationhas already begun in the vertebral b
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