The development of the human body; a manual of human embryology . ea over whichthe cloacal endoderm is in contact with the ectoderm toform the cloacal membrane (Fig. 156, cm) lies a little infront of the actual endof the archenteric cylin-der, the portion of thelatter which lies poste-rior to the membraneforming what has beentermed the post-anal gut 0.(). This diminishesin size during develop-ment and early disap-pears altogether, and thepouch-like fold seen inFig. 156 between the in-testinal portion of thearchenteron and the al-lantoic stalk (al) deepen-ing until its floor coniesinto cont
The development of the human body; a manual of human embryology . ea over whichthe cloacal endoderm is in contact with the ectoderm toform the cloacal membrane (Fig. 156, cm) lies a little infront of the actual endof the archenteric cylin-der, the portion of thelatter which lies poste-rior to the membraneforming what has beentermed the post-anal gut 0.(). This diminishesin size during develop-ment and early disap-pears altogether, and thepouch-like fold seen inFig. 156 between the in-testinal portion of thearchenteron and the al-lantoic stalk (al) deepen-ing until its floor coniesinto contact with thecloacal membrane, the cloaca becomes divided into a ventral portion, withwhich the allantois and the primitive excretory ducts (w)are connected, and a dorsal portion which becomes thelower end of the rectum. This latter abuts upon thedorsal portion of the cloacal membrane, and this event-ually ruptures, so that the posterior communication ofthe archenteron with the exterior becomes rupture, however, does not occur until a compara-25. 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-
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
