The development of the human body; a manual of human embryology . l under discussion, some authors believing theLanghans cells to be mesodermal, while others, admittingthat they are ectodermal, maintain the view that the syn-cytium is really maternal tissue. The view here presented ismost in accord with the more recent observations (Minot,Peters). As development proceeds the villi, which are at firstdistributed evenly over the chorion frondosum, areseparated into groups termed cotyledons (Fig. 69), bythe growth into the intervillous space of trabecules from 146 THE DEVELOPMENT OF THE HUMAN BOD
The development of the human body; a manual of human embryology . l under discussion, some authors believing theLanghans cells to be mesodermal, while others, admittingthat they are ectodermal, maintain the view that the syn-cytium is really maternal tissue. The view here presented ismost in accord with the more recent observations (Minot,Peters). As development proceeds the villi, which are at firstdistributed evenly over the chorion frondosum, areseparated into groups termed cotyledons (Fig. 69), bythe growth into the intervillous space of trabecules from 146 THE DEVELOPMENT OF THE HUMAN BODY. the walls of the uterus, the villous roots of attachmentbecoming connected with these septa as well as withthe general uterine wall. The ectoderm of the villi alsoundergoes certain changes with advancing growth, thelayer of L,anghans cells disappearing except in small areasscattered irregularly in the villi, and the syncytium,though persisting, undergoes local thickenings which de-generate more or less extensively into fibrin-like sub-stance(Fig. 68, B, cf).. Fig. 69.—Mature Placenta after Separation from the Uterus. c, Cotyledons; ch, chorion, amnion, and decidua vera; um, umbilical cord.—(Kollmann.) The changes which occur during the later stages ofdevelopment in the chorion are very similar to those de-scribed for the villi. Thus, the mesoderm thickens, itsoutermost layers becoming exceedingly fibrillar in struc-ture, while the ectoderm differentiates into two layers,the outer of which is syncytial while the inner is cellular,and later still, as in the villi, the syncytial layer degener-ates in irregular patches into a peculiar form of fibrin THE H7 which is traversed by flattened anastomosing spaces andto which Minot has applied the name canalized fibrin(Fig. 70).The Deciduae.—In connection with the phenomenon of ,*?&&???? ?*? ,.*&& mes
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
