The development of the human body; a manual of human embryology . d since the cessation offeeding (Fig. 91, B); and if this interval amount to four months,it will be found that the thickness of the uncolored bone be-tween the red bone andthe marrow cavity willhave greatly diminished(Flourens). The Development ofthe Skeleton.—Embryo-logically considered, theskeleton is composed oftwo portions, the axialskeleton, consisting of theskull, the vertebrae, ribs,and sternum, developingfrom the sclerotomes ofthe mesodermal somites,and the appendicularskeleton, which includesthe pectoral and pelvicgirdl
The development of the human body; a manual of human embryology . d since the cessation offeeding (Fig. 91, B); and if this interval amount to four months,it will be found that the thickness of the uncolored bone be-tween the red bone andthe marrow cavity willhave greatly diminished(Flourens). The Development ofthe Skeleton.—Embryo-logically considered, theskeleton is composed oftwo portions, the axialskeleton, consisting of theskull, the vertebrae, ribs,and sternum, developingfrom the sclerotomes ofthe mesodermal somites,and the appendicularskeleton, which includesthe pectoral and pelvicgirdles and the bones ofthe limbs, and which arises from the mesenchyme of the somatic will be convenient to consider first the developmentof the axial skeleton, and of this the differentiation of thevertebral column and ribs may first be discussed. The Development of the Vertebrae and Ribs.—Themesenchyme formed from the sclerotome of each meso-dermic somite grows inward toward the median line andforms a complete investment for the notochord, and, at. 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
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
