64 THE TROPHOBLAST AND ITS SURROUNDING BLOOD SPACES. 



the perivascular spaces and beneath the endothelium as well as 

 into the lumen of the blood vessels. All the giant cells which 

 have been found by some observers in the decidua, in this stage 

 of development of the ovum, are to be considered cells derived 

 from the syncytium. (Compare my identical findings in Fig. 4). 

 They have become separated from a pedicle at first existing and 

 then even in a series of sections show the character of isolated 

 cells. Often, however, they remain attached to the syncytium 

 from which they originate, and then only by mistake can be pro- 

 nounced giant cells." 



According to Marchand (pg. 262) the developing ovum reacts 

 upon the surrounding uterine inucosa like a malignant growth, 

 it "eats its way" into the mucosa as Graf v. Spec has demon- 

 strated for the earliest stage of the ovum of the guinea pig. 

 Other claims of Marchand need not be considered here since 

 the ova described by him are much older, two of them being 

 in quite a defective condition. 



The ovum described by Friolet and estimated to be from three 

 to four weeks old also seems of limited value in a consideration 

 of the very early stage. He agrees in all main points with 'Peters. 



Herrmann and Stolper have made exhaustive researches con- 

 cerning the ovum of the guinea pig and have arrived at the fol- 

 lowing conclusions: "1. In the guinea pig there exists but one 

 kind of syncytium and this is positively fetal, having developed 

 from the Anlage of the placenta. 2. There exists definite rela- 

 tions between the syncytium and maternal vessels ; and, 3. The 

 villus of the placenta of the guinea pig in a certain stage of de- 

 velopment, exactly like in the human placenta, shows the char- 

 acteristic double layer of epithelial cover." Thus the similarity 

 between mine and their findings is obvious. 



Concerning the very meritorious work of Webster, it must be 

 stated that in the main it presents a clear survey of all the findings 

 which have been made in all the various months of pregnancy, 

 but does not deal with any personal investigation of a new young 

 ovum. 



Beneke, who has examined a considerably older ovum (4.2x 

 2.2x1.2 mm.) with an embryo 1.86 mm. long, comes to deduc- 

 tions which are identical with Peters' and those of mine. In the 

 main he confirms the views of Van Heukelom, Peters, Marchand 

 and others concerning the structure of the trophoblast. He also 

 considers the syncytial giant cells as originating from fetal ecto- 

 blast. He did not succeed in differentiating a Symplasma glandu- 

 lare, conjunctivum and cndothclialc from fetal syncytium as has 

 been done by Bonnet. The synctium displaces the endothelial 



