The development of the human body; a manual of human embryology . Fig. 155.—Reconstruction op theAnterior Portion of an Embryo of MM. ab, Aortic bulb; h, heart; o, auditorycapsule; op, optic evagination; pm,pharyngeal membrane.—(His.) 298 THE DEVELOPMENT OF THE HUMAN BODY. tively late period of development, until after the embryohas reached the fetal stage; nor does the position of themembrane correspond with the adult anus, since laterthere is a considerable development of mesoderm aroundthe lower end of the rectum, which bulges out, as it were,the regions immediately surrounding the mem
The development of the human body; a manual of human embryology . Fig. 155.—Reconstruction op theAnterior Portion of an Embryo of MM. ab, Aortic bulb; h, heart; o, auditorycapsule; op, optic evagination; pm,pharyngeal membrane.—(His.) 298 THE DEVELOPMENT OF THE HUMAN BODY. tively late period of development, until after the embryohas reached the fetal stage; nor does the position of themembrane correspond with the adult anus, since laterthere is a considerable development of mesoderm aroundthe lower end of the rectum, which bulges out, as it were,the regions immediately surrounding the membrane, pro-. nc Fig. 156.—Reconstruction op the Hind End op an Embryo mm. Long. al, Allantois; b, belly-stalk; cl, cloaca; cm, cloacal membrane; i, intes-tine; n, spinal cord; nc, notochord; , post-anal gut; ur, out-growth to form ureter and metanephros; w, Wolffian duct.—(Keibel.) ducing a short ectodermal addition to the rectum, theend of which is the definitive anus. It will be noticed that the digestive tract thus formedconsists of three distinct portions, an anterior, short, ecto-dermal portion, an endodermal portion representing theoriginal archenteron, and a posterior short portion whichis also ectodermal. The differentiation of the tract into THE MOUTH-CAVITY. 299 its various regions and the formation of the various organsfound in relation with these may now be considered. The Development of the Mouth Region.—The deepeningof the oral sinus by the development of the first branchialarch and its separation into the oral and nasal cavitiesby the development of the palate have alr
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
