HYDATIFORM DEGENERATION IN UTERINE PREGNANCY. 221 



Although hydatiform villi covered by a single layer of rather small cells of the 

 nature of Langhans cells, sometimes without visible cell boundaries, frequently 

 were seen, villi covered by typical syncytium only were never seen. The single 

 layer present, although syncytial in places, suggested Langhans cells rather than 

 the real syncytium. Moreover, since the cells of the Langhans layer usually were 

 smaller rather than larger than normal, it follows from this alone that their pro- 

 liferation nevertheless must have been marked, in order to completely cover the 

 enlarged villus, in spite of the fact that the layer remained single-celled. Were 

 this not the case the extraordinary increase in size which accompanies the formation 

 of large hydatid cysts could not possibly occur without rupture of the covering 

 layer. 



Not infrequently proliferation of the epithelium without increase in thickness 

 may manifest itself in another way. The caliber of the villi in the earlier stages of 

 hydatiform degeneration sometimes does not increase much and no thickening of 

 the proliferating epithelium is noticeable, yet the latter shows marked proliferation. 

 Under these circumstances, the borders of the villi and of the chorionic epithelium 

 may appear extraordinarily sinuous, as illustrated in figure 117, and epithelial 

 invaginations from opposite sides may in rare instances meet in the center, as 

 indicated in figure 118, and, by fusion, completely isolate a portion of the stroma. 

 It is usually in these cases of very sinuous epithelium that the epithelial invagi- 

 nations sometimes become constricted, leaving a closed epithelial vesicle or a 

 nodule of epithelium attached to a stalk or wholly isolated within the stroma, as 

 shown in figures 119 and 120. All stages in this process of vesicle formation were 

 found, and rarely also extensions of epithelial sprouts, as described by Neumann 

 (1897) and others, were seen, portions of which had become isolated in the stroma 

 to appear later as typical syncytial giant cells. These facts, too, would seem to 

 throw a sidelight upon the origin of the syncytium for those to whom this ques- 

 tion is still an open one. 



All these things abundantly testify to the activity on the part of the epithelium 

 in many hydatiform moles, even when thickening of it is absent, but they are of 

 diagnostic value only if present, and I wish to emphasize again that they may be 

 wholly absent and also unrecognizable in the early stages. Moreover, the degree 

 of epithelial proliferation varies greatly, as illustrated in figures 112, 121, and 122. 



Until I am able to learn more about the structure of normal villi in various 

 stages of development, I am not willing to commit myself regarding the earliest 

 changes in hydatiform degeneration. These may be unrecognizable with present 

 methods. However, it is possible to say that in young conceptuses the disappear- 

 ance of the capillaries, which was regarded as a posisible cause for the development 

 of hydatiform mole by Hewitt (1860, 1861), and which was emphasized later 

 by Hahn (1864), Maslowsky (1882), and also by others, undoubtedly is a very 

 early and possibly the very earliest noticeable change in some cases. I do not imply 

 that death of the embryo is the cause of this disappearance, as Hewitt held, and 

 I am not ready to say that the vascular change is the very earliest one in all cases. 

 This would imply that hydatiform degeneration under no circumstances can 



