. An American text-book of obstetrics. For practitioners and students. Visceralmesoderm. Notochord. Somite. Gut entoderm. Fig. 116.—Transverse section of a sixteen and a half day sheep embryo possessing six somites (Bonnet). the third month the external sexual characteristics of the fetus are establishedbeyond doubt. Imperfect development, especially faulty union, of certainparts of the primitive genitalia produce the conditions which give rise to ap-parent hermaphroditism : true hermaphrodites, while not impossibilities, are Ectoderm Closing-neural Amnion. Parietalmesoderm. Cell-mass/
. An American text-book of obstetrics. For practitioners and students. Visceralmesoderm. Notochord. Somite. Gut entoderm. Fig. 116.—Transverse section of a sixteen and a half day sheep embryo possessing six somites (Bonnet). the third month the external sexual characteristics of the fetus are establishedbeyond doubt. Imperfect development, especially faulty union, of certainparts of the primitive genitalia produce the conditions which give rise to ap-parent hermaphroditism : true hermaphrodites, while not impossibilities, are Ectoderm Closing-neural Amnion. Parietalmesoderm. Cell-mass/orWolffian body. Celom. Mesothelium. Primitiveendothelium. Visceralmesoderm. 117.—Transverse section of a fifteen and a half day sheep embryo possessing seven somites (Bonnet). among the rarest malformations, since in them the formation of true sexualorgans of both sexes must take place in the same individual. 10. Development of the Nervous System.—The initial stage in the pro-duction of the great cerebro-spinal nervous axis is the formation of the medul-lary folds and groove (Figs. 116, 117), one of the earliest of the fundamental 126 AMERICAN TEXT-BOOK OF OBSTETRICS. processes in the development of the embryo. At the thirteenth day the neuralgroove is widely open throughout its extent; two days later, by the beginning of the third week, the groove has becomeconverted into a closed canal by the ap-proximation of the thickened neuralplates along the dorsal mid-line. Thecephalic extremity of the neural canal, Anterior brain-vesicle
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectobstetrics, bookyear1
