SECRETORY FUNCTIONS IN HUMAN PLACENTA 535 



not come out into the intervillous spaces together with those 

 of the syncytium layer? In a word, since the Langhans' layer 

 is entirely closed against the mother's body by the syncytium 

 layer in the early stage of pregnancy, it would follow that the 

 secretions are entirely in the service of the embryo, but after 

 that it is probable that a part of them are taken also by the 

 mother's body. 



The function of secretion of the Langhans' cells, just like 

 the syncytium layer, is active in the main almost from the 

 first stage to the end of the fourth month of pregnancy, though 

 in the second and third months it is very active, suddenly 

 subsiding with the fifth month. In the Langhans' islet it con- 

 tinues still longer and commonly gradually subsides after the 

 sixth or seventh month. 



The epithelium of villi is located between the circulation of 

 the mother's body and that of the embryo, and it is for this rea- 

 son presumed that it must be an organ which takes nutrition 

 for the embryo, as has been commonly held in literature, but 

 that such is a groundless assumption must be quite clear from 

 my histological observations given above. And, besides, there 

 are some important reasons which prove the utter fallacy of 

 this theory. It is in the first to third months of pregnancy 

 that the growth of the epithelium of villi is most active. If 

 the functions of the alimentary organ for the embryo be assign- 

 ed to it, the epithelium of the villi should go on developing most 

 vigorously, but the fact is quite the reverse, and it retrogrades 

 and becomes thin in the second half of pregnancy, and accord- 

 ingly the decline of functions is brought about. This is one of 

 the absurdities. And in the eighth month of pregnancy, when 

 the embryo calls for a still greater increase in the supply of its 

 nutrition the capillary blood vessels of vilh increases suddenly, 

 as was mentioned above, and early in this stage the epithe- 

 lium of villi becomes remarkably regressive and falls into decay, 

 so that the embryonal circulation of the villi is separated 

 from that of the mother only by a thin membrane like endo- 

 thelium, undoubtedly it being quite easy for both to allow the 

 interchange of materials between them. In other words, the 



