22 



walls of the womb. At intervals, fine bloodvessels course up between them, 

 and, reaching the mucous surface, surround the tubules with a capillary network. 

 But when fecundation is effected vascular turgessence at once sets in, producing 

 rapid growth and development of the membrane of the follicles especially ; 

 and, coming in contact with this highly vascular and tumified surface as it leaves 

 the Fallopian tube, the ovum is rapidly incorporated with it, by means of the 

 shaggy villosities which are thrown out from the outer surface (Fig. 14, ..), 



FIG. 14. OVUM OF THE RABBIT, from a Graaflan follicle J 6 of an inch in diameter. A, epithe- 

 lium of the ovum; 6, zona pellucicla, with radiating striations (vitelline membrane); 

 c, germinal vesicle; rf, germinal spot; e, vitellus. (After Waldeyer.) 



FIG. 15. IMPREGNATED UTERI'S, showing connection between villosities of chorion and decidual 

 membranes. (After Dalton.) 



which grow into the expanded orifices of the tubules, and function as temporary 

 villi for pumping the abundant albuminous secretions of the glands in the in- 

 terior of the ovum. Of course, they contain all the elements of tissue struc- 

 ture. With the ingrowing of the shaggy tufts of the chorion in the follicles, 

 the mucous membrane expands around the ovum for bringing the follicles in 

 contact with every portion of the chorion till the whole is completely enclosed, 

 forming what is known as decidua reflexa, while that portion of the membrane 

 with which it first came in contact, in immediate relation with the muscular 

 walls, constitutes decidiia, vera, the part that enters the structure of the 

 placenta which is subsequently formed. At this time the villosities of the 

 chorion project into the uterine follicles in every direction (Fig. 15), but as 

 growth proceeds, aiirl more and more nutriment is needed in the embryo, the 

 villi in relation with decidua vera become vascular, while those in relation 

 with decidua reflexa are atrophied, in consequence of which this portion of the 

 chorion becomes bald. Finally, the transformations which occur in the placenta 



