THE TROPHOBLAST AND ITS SURROUNDING BLOOD SPACES. 61 



structure and the lining of the trophoblast processes with syn- 

 cytium exactly the same as I saw them. He says on page 49: 

 "From the simple cuboidal cells of the central portion of the 

 trophoblast one can successively follow, towards the surface, their 

 transition into the large syncytial formations/' 



"Those blood lacunae which on their proximal surface carry a 

 layer of ectoblast cells, are almost completely lined by a thin 

 layer of protoplasm in which cell membranes not discernible and 

 in which nuclei are visible, arranged in rows. In transverse sec- 

 tions these nuclei appear spindle shaped, in oblique and longi- 

 tudinal sections they look flat, often irregularly bent and in their 

 appearance seem identical with the nuclei previously described 

 in the peripheral layer of the ectoblast. This thin protoplasma 

 coat which in the central portion of the blood lacunae resembles 

 a layer of epithelium, continues on the lateral walls of the lacunae, 

 thus enclosing the trophoblast columns." 



Peters therefore also finds the blood within the lacunae sep- 

 arated from the trophoblastic excrescences and columns, espe- 

 cially within the arches, by a syncytial lining. 



As far as that area of the decidua compacta is concerned, 

 which immediately adjoins the trophoblast (Umlagerungszone 

 of Peters pg. 52), here surrounding the entire ovum, especially 

 on the side of the serotina, greatly dilated maternal blood vessels 

 and a large number of transverse sections through glands are 

 seen,. The uterine mucosa here is not only edematous, but also 

 abundantly infiltrated with blood elements. 



Further away from the ovum in Peters' specimen (Plate I) a 

 large endothelial tube is visible from which a number of larger 

 and smaller vessels branch off. These encircle the ovum like 

 meridians the globe. "They communicate with the blood lacunae 

 of the trophoblast near the oyular pole, often only after having 

 first passed through a part of the 'Umlagerungszone' or through 

 intermediate layers lying between it and. the compacta. In other 

 places these vessels after only a short course open into the la- 

 cunae at points near the serotina." 



As regards the relation of the trophoblast to the surrounding 

 capillaries and their endothelial tubes, Peters' investigations (pg. 

 59) show that the trophoblastic processes do not bore their way 

 into the endothelial walls as I have described, but that the blood 

 has actively broken into the trophoblast. This condition Peters 

 has depicted in that excellent illustration, Fig. 23, v Plate A, to 

 which I cannot furnish an equal from any one of my sections. 

 I have only been able to observe, as stated above, that at first the 

 ovule lies in a premenstrual extravasate of blood in the mucosa, 



