220 



PHYSIOLOGY 



CHAP. 



chorion assumes the appearance of a smooth membrane (chorion 

 laeve}\ in the region of the placental decidua,<on the contrary, the 

 villosities become hypertrophic and longer, ramify and multiply 

 (chorion frondosum). This flourishing vegetation of the chorion 



FIG. 83. Gravid uterus at five months. Longitudinal section. Half natural size. (From a 

 preparation of the Obstetrical Clinic at Bale.) a, decidua vera ; 6, chorion and amnion ; 

 c, marginal substance of placenta ; d, internal orifice ; e, external orifice ; /, vagina. 



in the seat of the placenta is shown in Fig. 82, but is more obvious 

 in Figs. 86, 87, and 88. 



The origin of the epithelial covering of the villus is at present 

 a disputed point. The syncytium and the cellular stratum of 

 Langhans represent a single element, inasmuch as the syncytium 

 may be transformed into the cells of Langhans and vice versa. 



