THE EIAXLAGE AND THE OVULAR CHAMBER (EIKAMMER.) 53 



the condition of the endometrium at the time when the ovum is 

 entering it. We assume that the most suitable time for implan- 

 tation of the fertilized ovum is the last few days preceding the 

 first missed menstruation. 



In the premenstrual stage the mucosa is not only congested, 

 but as is shown in Fig. 25, Plate XV, permeated by extra vasated 

 blood. According to Gebhard, a second stage follows character- 

 ized by an accumulation of large extravasates in irregular lacunae 

 of the mucosa. As a result of the rupture of some capillaries 

 beneath the surface epithelium, subepithelial haematomata are 

 formed from which, after slight detachment of the epithelium, 

 blood escapes into the uterine cavity as -the visible menstrual 

 flow. 



The blood which has escaped from the capillaries thus spreads 

 both beneath the epithelium and in the deeper layer of the mu- 

 cosa as an irregular extravasate and also enters the glands (Geb- 

 hard). One must therefore bear in mind that this free blood lies 

 chiefly in artificial cavities, not lined by an endothelium. 



The fertilized ovum which in the premenstrual stage, i. e., 'be- 

 fore the menstrual flow has appeared, is about to enter the uter- 

 ine mucosa, finds a markedly loosened tissue infiltrated with blood 

 and will hardly experience any difficulty to pass through or push 

 aside the loosened surface epithelium. 



When the ovum has penetrated the superficial layers of the en- 

 dometrium it is in a tissue permeated by the extravasates just 

 described and lies either free in one of these extravasates or at 

 least at the edge of one of them in the tissue of the mucosa. At 

 any rate, we seem justified in assuming, that the fertilized ovum, 

 immediately after its implantation, displays great vitality, that it 

 will develop and that above all things it will attempt to fasten 

 itself, which probably is most quickly accomplished by extending 

 the first trophoblast processes. 



My idea is, that the embedded ovum, for a very short time, 

 either partly or completely, lies in a blood extravasate. Since 

 these blood spaces have formed as a result of a rupture of capil- 

 laries they are devoid of a continuous endothelial lining and 

 show an endothelium only at places where ruptured capillaries 

 enter. 



The ovum thus floats, possibly only for the first few hours, in 

 a blood cavity, i. e., it is from the very beginning surrounded 

 by a maternal blood from which it receives its nutriment. When 

 and how quickly the entrance gate is closed again we do not 

 know, it is possible that this, process varies as to mode and time. 

 Many observations, however, suggest that the closure is effected 



