214 



PHYSIOLOGY 



CHAP. 



we will pause to explain the manner in which the ovum grafts 

 itself in the uterine mucosa with which it has come into contact. 



According to Minot, the ovum reaches the uterus on the 

 eighth day after fecundation, when it is about 0'2 mm. in diameter, 

 has already undergone the process of segmentation and reached the 

 morula stage. According to the observations of von Spee, the ovum 

 of the guinea-pig, when it arrives in the uterine cavity, provokes 

 therein a marked hypertrophy of the epithelial covering; a breach 

 is made at the point of contact, and the ovum sinks into a small 

 depression formed in the sub-epithelial connective tissue (Fig. 77). 



Fio. 77. Planting of ovum of guinea-pig in uterine mucosa. (von Spee.) The ovum (1) passes 

 through the uterine epithelium - f 2, sinks through the opening in the epithelium into a 

 depression hollowed out in the sub-epithelial connective tissue ; 3, connective tissue cells ; 

 4, capillary vessel; 5, cavity within ovum formed by cells of segmentation, both large 

 and round. 



We do not as yet possess any actual observation of the first 

 stages of the human ovum. The earliest studied by Keichert was 

 twelve to fourteen days old ; the ckorion, the most external 

 membrane of the ovum in the course of development, was already 

 fairly well developed, was provided with villosities on a circular 

 zone, and contained a rough outline of the embryo (Fig. 78). 



As to the way in which the human ovum grafts itself on 

 the uterus we have only Peter's observations made on a woman 

 who had committed suicide a few days after the cessation of 

 menstruation. The ovum looked like a prominence about the 

 size of a hemp-seed on the uterine mucosa. The posterior wall 

 of the mucosa was considerably thickened. The grafting had 

 taken place in the space between two glands. At the point 



