234 STUDIES ON PATHOLOGIC OVA. 



tion of the venous return, for such a condition necessarily would be rare and not 

 common. Moreover, this condition of necessity would have to arise before and not 

 after the death of the embryo and detachment of the chorionic vesicle. As in one 

 of the cases of Hiess (1914), such a specimen also should contain blood-vessels; 

 for, as emphasized also by Ballantyne and Young (1913), the hydatiform villus 

 is not merely an edematous villus. 



That any one at all familiar with hydatiform degeneration, in its earlier as 

 well as its later forms, could, upon gross and microscopic examination, confuse it 

 with maceration changes in a fairly well preserved specimen in any but its very 

 earliest stages does not seem possible to me. Normal villi contain capillaries, not 

 to mention other things characteristic of them. Hydatiform villi, on the contrary, 

 do not contain them, or only very rarely so, and only in the early stages. When a 

 villus becomes hydatiform that is, when liquefaction of the stroma occurs this 

 liquefaction appears in more or less restricted portions of the villus, thus giving rise 

 to the long fusiform and later spherical vesicles so characteristic of hydatiform 

 mole. But when a villus becomes macerated the change is general, and usually is 

 noticeable also in the embryo and chorionic membrane itself, or at least within the 

 epithelium. The latter usually is lifted from the stroma here and there, the caliber 

 of the entire villus is increased, and the capillaries and the stroma show maceration 

 changes as the villus becomes more translucent. This increase in caliber of the 

 entire villus is not due to local liquefaction of the stroma, but to the pseudo-edema 

 occurring in a villus of normal structure and form. In hydatiform moles, on the 

 contrary, the epithelium not only is firmly attached but usually hyperactive. The 

 changes characteristic of hydatiform degeneration may and often do appear in the 

 villi while they are still implanted, and not only after the chorionic vesicles are 

 detached. This does not imply, however, that the villi of a detached hydatiform 

 mole can not also undergo maceration changes. They frequently do so, and 

 it is in such cases as these that differentiation may be difficult or impossible, espe- 

 cially if it is to be made from an examination of ill-preserved fragments only. The 

 same thing is true also of the villi in the early stages of hydatiform degeneration 

 and maceration, especially when the latter masks the former. The difficulty would 

 be still greater in case of whole chorionic vesicles which are almost completely 

 dissolved, leaving only a shadow picture formed by a coagulum without nuclei, 

 which nevertheless may retain almost perfectly the form of the chorionic vesicle 

 and of the individual villi. It may long be impossible to differentiate such cases 

 as these, but they form only a relatively small proportion of the whole. The many 

 cases both of uterine and tubal chorionic vesicles which still were implanted and 

 show exceedingly fine instances of hydatiform degeneration, as well as the many 

 splendid examples of groups of villi which were still implanted in the tube or in the 

 decidua, and which were equally good examples of hydatiform degeneration, leave 

 no room for doubt as to the surprising frequency in the occurrence of this con- 

 dition, even after due allowance is made for the doubtful cases. 



A careful examination of the few cases from the literature which have been 

 regarded as instances of pseudo-hydatiform degeneration leave one wholly uncon- 



