The practice of obstetrics, designed for the use of students and practitioners of medicine . Fig. 66.—Sagittal Section of Fig. 65. Showing in addi-tion the allantoic process, the complete amnion, am., witha slight extension toward the chorion, c, and the thickeningof the mesoderm, m., where the heart will develop, ,Medullary plate; , heart fold; , chorionic viUi; ,allantois stalk; , primitive streak; , allantoic canal;, yolk sac; en., entoderm; v., vessels; , Fig. 67.—Cross-section ofFig. 65. Shows the ecto-derm forming the medul-lary folds and
The practice of obstetrics, designed for the use of students and practitioners of medicine . Fig. 66.—Sagittal Section of Fig. 65. Showing in addi-tion the allantoic process, the complete amnion, am., witha slight extension toward the chorion, c, and the thickeningof the mesoderm, m., where the heart will develop, ,Medullary plate; , heart fold; , chorionic viUi; ,allantois stalk; , primitive streak; , allantoic canal;, yolk sac; en., entoderm; v., vessels; , Fig. 67.—Cross-section ofFig. 65. Shows the ecto-derm forming the medul-lary folds and groove andat the right thinning toform the amnion, am.,Amnion; ek., ectoderm;ct., amniotic mesoderm;g., meeting point of soma-topleure and splanchno-pleure; df., mesoderm ofyolk sac; b, b, b, blood-vessels; en., entoderm; n,blastopore; d, cavity ofyolk-sac, — (After GrafSpee.) common landmark in early development throughout the vertebrate series, marking the point from which the mesoderm takes its origin. The neurenteric canal is seen in a very early human ovum described by Graf Spee (Fig. 65). According to Mall, its last remnant is distinct until adult structures are sufficiently developed to determine its relative location, it being at the level of the first rib. This one fact shows that the structures derived from the head and neck are the earliest to be laid down, the whole of the trunk and limbs being of later formation. Formation of Primitive Organs.—The early embryology of organs has al
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectobstetrics, bookyear1
