The development of the human body; a manual of human embryology . W. Hubrecht: Studies on Mammalian Embryology II: The De-velopment of the Germinal Layers of Sorex vulgaris, QuarterlyJourn. of Microsc. Science, xxxi, 1890. F. Keibel: Studien zur Entwickelungsgeschichte des Schweines, Mor- pholog. Arbeiten, in, Mitsukuri and C. Ishikawa: On the Formation of the GerminalLayers in Chelonia, Quarterly Journ. of Microsc. Science, xxvil, 1887. LITERATURE. 81 E. SelEnka: Studien iiber Entwickelungsgeschichte der Thiere,4tes Heft, 1886-87; 5tes Heft, Sobotta: Die Befruchtung und Fur
The development of the human body; a manual of human embryology . W. Hubrecht: Studies on Mammalian Embryology II: The De-velopment of the Germinal Layers of Sorex vulgaris, QuarterlyJourn. of Microsc. Science, xxxi, 1890. F. Keibel: Studien zur Entwickelungsgeschichte des Schweines, Mor- pholog. Arbeiten, in, Mitsukuri and C. Ishikawa: On the Formation of the GerminalLayers in Chelonia, Quarterly Journ. of Microsc. Science, xxvil, 1887. LITERATURE. 81 E. SelEnka: Studien iiber Entwickelungsgeschichte der Thiere,4tes Heft, 1886-87; 5tes Heft, Sobotta: Die Befruchtung und Furchung des Eies der Maus, Archiv ]v,r mikrosk. Anat., xlv, Sobotta: Die Furchung des Wirbelthiereies, Ergebnisse der Anat. und Entwickelungsgeschichte., vi, Will: Beitrage zur Entwicklungsgeschichte der Reptilien, Zoolog. Jahrbilcher, Abth. fiir Anat., vi, 1893. CHAPTER III. THE DEVELOPMENT OF THE EXTERNALFORM OF THE HUMAN EMBRYO. The youngest human ovum at present known is thatdescribed by Peters. It was taken from the uterus of a am crn-. Fig. 35.—Section of Embryo and Adjacent Portion of an Ovum of 1 MM. am, Amniotic cavity; ce, chorionic ectoderm; cm, chorionic mesoderm;ec,embryonic ectoderm; en, endoderm; m, embryonic mesoderm; ys,yolk-sac.—{Peters.) woman who had committed suicide one calendar monthafter the last menstruation, and it measured about i diameter. The entire inner surface of the trophoblast(Fig. 35, ce) was lined by a layer of mesoderm (cm), which, 82 THE EXTERNAL FORM OF THE BODY. 83 on the surface furthest away from the uterine cavity, wasconsiderably thicker than elsewhere, forming an area ofattachment of the embryo to the wall of the ovum. Inthe substance of this thickening was the amniotic cavity(aw), whose roof was formed by flattened cells, which, atthe sides, became continuous with a layer of columnar cellsforming the floor of the cavity and constituting the em-bryonic ectoderm (ec). Immediately below this was a
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