THE SECOND WEEK. 473 



entire uterus was lined by a decidua, described as not differing 

 in any special manner from an ordinary menstrual decidua, and 

 forming the usual ridge-like projections into the cavity of the 

 uterus. To one of these ridges, on the dorsal surface of the 

 fundus of the uterus, the ovum was attached, the decidua 

 spreading over it as a thin layer so as to completely encapsule it 

 (cf. Fig. 175). The marginal villi were ^ 



described and figured by Reichert as 

 penetrating a little distance into the 

 enlarged uterine glands. 



In the ovum itself there was no 

 indication of primitive or neural grooves, 



nor of any other part of the embryo. IlG - . 174> Diagram- 



i> -i ^ i matic section of 



Ihe wall of the vesicle was described by Reichert's Ovum. 



Reichert as consisting of a single layer (From His.) x o. 



, i -iiTi n i n a, the embryonal area. 



of flattened epithelial cells, prolonged 



outwards to form the hollow villi. In the circular patch on 

 the uterine surface, spoken of as the germinal or embryonal 

 area, a second or inner layer of finely granular nucleated cells 

 was present. The cavity of the vesicle was occupied by a 

 gelatinous fluid, traversed by a network of fibres, and con- 

 taining within it a rounded body attached to the germinal area. 



Lining the whole vesicle was a second, fairly coherent 

 membrane, with which the fibres were continuous. By Reichert 

 this second membrane, the network of fibres, and the central 

 rounded body were all alike considered to be artificial products, 

 due to coagulation of the fluid contents of the vesicle by the 

 alcohol in which the specimen was preserved. 



Ova of similar appearance, and of apparently about the same 

 age, have been described by Wharton Jones, Breuss, Kollmann, 

 and others ; and in none of these cases was any trace of an 

 embryo present. 



The position held by the ovum in relation to the uterus, in 

 the case recorded by Kollmann, is shown in Fig. 175. The 

 whole uterus was lined by a decidual membrane, DV ; this was 

 greatly thickened about the middle of the ventral wall, forming 

 the decidua serotina, DW, to which the ovum, CV, was attached ; 

 the decidua extending over the ovum so as to completely en- 

 capsule it. The ovum itself was in the form of a hollow, thin- 

 walled vesicle, with short branched villi projecting from its 



