The development of the human body; a manual of human embryology . Fig. 92.—Transverse Sectionthrough the intervertebralPlate of the First CervicalVertebra of a Calf Embryo MM. be1, Intervertebral plate; m4, fourthmyotome; s, hypochordal bar; XI,spinal accessory nerve.—{Froriep.) I 82 THE DEVELOPMENT OF THE HUMAN BODY. the same time, sends a wing dorsally on each side of themedullary canal, so that this, as well as the notochord,becomes enclosed by a series of mesenchymatous masses,each of which is separated from its predecessor and suc-cessor by a plate of more densely arranged mesenchym
The development of the human body; a manual of human embryology . Fig. 92.—Transverse Sectionthrough the intervertebralPlate of the First CervicalVertebra of a Calf Embryo MM. be1, Intervertebral plate; m4, fourthmyotome; s, hypochordal bar; XI,spinal accessory nerve.—{Froriep.) I 82 THE DEVELOPMENT OF THE HUMAN BODY. the same time, sends a wing dorsally on each side of themedullary canal, so that this, as well as the notochord,becomes enclosed by a series of mesenchymatous masses,each of which is separated from its predecessor and suc-cessor by a plate of more densely arranged mesenchyma-tous cells (Fig. 92, be2). These intervertebral plates are. Fir,. 93.—Longitudinal Section through the OeciriTAL Region andUpper Cervical of a Calf Embryo of mm. bas, Basilar artery; ch, notochord; JCc1-4, vertebral centra; Ic2-*, inter-vertebral disks; occ, basioccipital; Sc-*, hypochordal bars.—(Froriep.) portions of the intermuscular septa which occupy the inter-vals between adjacent mesodermie somites and are formedof cells which have wandered from the anterior and poste-rior surfaces of the somites. At first, then, the invest-ment of the notochord and medullary canal is by a seriesof alternating segmental and intersegmental cellular THE VERTEBR/E. I 83 masses, and the first stage in the development of the verte-brae may be termed the cellular stage. In the second or cartilaginous stage the mesenchymebecomes converted into cartilage in certain definite re-gions. The portions of sclerotomic mesenchyme whichsurround the notochord become chondrified and form thevertebral centra (Fig. 93, Kc), these structures beingtherefore
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
