Embryonic Development in Man. 385 



Peters, in his ease, has shown how the ovum did not make its 

 way into a gland duct, but had eaten its path into the decidua and 

 he opposed the old theory as to the formation of the decidua reflexa. 

 He, however, conceded the desirability of demonstrating the mode of 

 entrance of the ovum in more than one case examined in situ. 



Our own case, offering in some regards even better conditions, 

 namely, almost absolute certainty of the absence of all pathologic 

 deviations from the normal type, fully confirms the view of Peters 

 of the mode of implantation of the ovum and of the erroneousness 

 of the older theories. Both the Peters and our ovum show the cor- 

 rectness of Count von Spee's^^ hypothesis that the human ovum would 

 be found to behave in its method of implantation into the uterine 

 mucosa like the ovum of the guinea-pig. It was shown by von Spee 

 that the dividing blastoderm of the guinea-pig eats its way through 

 the uterine epithelium, into the connective tissue, causing here edema 

 and hyperemia. 



Exoccelom and Chorion Mesoderm. 

 The chorionic cavity or the exoccelom, as to its size and shape, 

 has been sufficiently described. The position of the embryonic 

 shield, yolk sac and allantois have also been indicated. Aside from 

 the "Keimanlage," the exoccelom shows in its interior a finely 

 granular, irregularly lumped material, which has stained intensely 

 with eosin. This material can be well seen in photomicrographs. 

 Figs. 24 and 25. It is responsible for the fact that the sections 

 of the embryo could not be photographed so that they appear on a 

 clear homogeneous background. What is seen in the sections with 

 reference to the eosin-staining granular material proves that the 

 exoccelom '^inter vitam" was filled with a watery fluid rich in coagu- 

 lable proteids. The strongly eosin-staining properties of the gran- 

 ular material may perhaps be due to an absorption of hemoglobin 

 indirectly derived from maternal sources. Towards the periphery, 

 that is, towards the lining chorion mesoderm, and running parallel 



"von Spee : Die Implantation des Meerschweincheneies. Zeitsclir. f. Morph. 

 n. Antbrop., 1901, Vol. Ill, p. 130; and Ueber die mensebl. Eilvammer, etc., 

 Verb, der Anat. Ges. zii Kiel, 1898, p. 196. 



