66 



IMBEDDING- OF OVUM 



it, as if pushed aside by the growing ovum, and there was absolutely no indication 

 that any gland-mouths opened into the cavity in the mucous membrane, nor 

 were there any traces of uterine epithelium lining it. These facts, which have 

 been recently confirmed in the ovum described by Leopold, clearly indicate that 

 the ovum is at a very early stage cut off from the general cavity of the uterus, 



FIG. 94. ANTERO-POSTERIOR SECTION OF THE GRAVID 

 UTERUS AND OVUM OF FIVE WEEKS : DIAGRAM- 

 MATIC. (Allen Thomson.) 



a, anterior, p, posterior uterine wall ; m, muscular 

 substance ; u, placed in the cavity of the uterus ; 

 g, the glandular layer of the decidua vera ; r, the 

 decidua capsularis ; s, decidua basalis ; c, cervix uteri ; 

 ch, chorion with its villi, which are more highly de- 

 veloped on the placental side ; e, the embryo enclosed 

 in the amnion, with the allantoic vessels passing along 

 a short allantoic stalk into the placenta, and the 

 umbilical vesicle lying free in the space between 

 amnion and chorion. 



FIG. 95. DIAGRAMMATIC SECTIONS OF THE UTERINE MUCOUS MEMBRANE, SHOWING THE CHANGES WHICH 

 THE GLANDS UNDERGO WITH THE SUPERVENTION OF PREGNANCY. (From Kundrat and Engelmann.) 



A. Diagram of the glands of the non-pregnant uterus ; m, muscular layer. B. Condition of the 

 glands at the beginning of pregnancy ; c, compact layer near free surface of decidua ; the glands are 

 here somewhat enlarged but not very tortuous, and the mucous membrane is rendered compact by 

 hypertrophy of the interglandular tissue ; sp, spongy layer, containing the middle portion of the 

 glands greatly enlarged and tortuous, producing a spongy condition in the mucous membrane ; 

 d, deepest portion of the glands, elongated and tortuous, but not much enlarged. 



not, however, as used to be supposed, by an upgrowth round it of the mucous 

 membrane, but in some different fashion. For a parallel we must look to those 

 cases among the lower mammals in which the blastocyst remains very small, 

 and becomes very early surrounded by decidual tissue. Such cases occur among 

 the Insectivora e.g. the hedgehog and also among the Cheiroptera ; but the nearest 



