212 STUDIES ON PATHOLOGIC OVA. 



In view of the prevailing opinion, I realize that these findings may seem 

 incomprehensible and perhaps incredible, unless it is distinctly borne in mind 

 that it is not stated that this incidence refers to the later months of pregnancy or to 

 term. What the incidence in the later months of pregnancy may be I do not know, 

 but I have called attention to an apparently well-founded belief that it is a rela- 

 tively rare condition, the estimates ranging from 1 in 2,000 to 1 in 728 or 300 cases. 



In regard to the incidence of hydatiform degeneration in uterine specimens, 

 it should also be remembered that the life, in contrast to the laboratory, incidence 

 for the entire period of gestation is higher, not only because the chorionic vesicles 

 were not included in many of the accessions and because others were too degenerate, 

 but because I have not as yet been able to recognize the very earliest stages with 

 entire certainty. Furthermore, many instances of hydatiform degeneration from 

 the early months of pregnancy, especially the first and second, are inevitably lost. 

 The increase due to these things would be offset somewhat, however, by the lower 

 incidence of hydatiform degeneration in specimens from the last months of preg- 

 nancy, relatively few abortuses from these months being contained in the Carnegie 

 Collection. 



To what extent the material in this collection is truly representative of actual 

 life conditions is difficult, if not impossible, to determine. This question could 

 be answered only if all the abortuses and material from abortions actually reached 

 physicians, and if the latter sent all of them to the laboratory. My own impression 

 so far is that the material representative of a sufficiently large community probably 

 would have a somewhat lower incidence, notwithstanding the fact that many 

 specimens, not only of hydatiform degeneration, but of abortuses in general, espe- 

 cially from the first month of pregnancy, are lost. However, since the presence of 

 hydatiform degeneration is especially common among early specimens, the inclusion 

 of these might raise the incidence for the whole period of gestation more than the 

 inclusion of all specimens (not excepting those of the last 3 months) would lower it. 

 But the result obtained would represent the incidence of hydatiform degenera- 

 tion in abortuses alone, and not that in all pregnancies. The latter could be 

 obtained only by including all gestations which end normally. If we accept 

 Pearson's (1897) estimate that approximately 40 per cent of all pregnancies end 

 prematurely, then the incidence of hydatiform degeneration among abortuses would 

 represent very nearly twice that in all pregnancies. Mall's (1908, 1918) estimate 

 of 20 per cent prenatal mortality, on the other hand, would give us an incidence 

 only one-fifth as great as that among abortuses. Hence, the actual life incidence 

 of hydatiform degeneration in all gestations would then be 1 in 10, as based upon 

 Pearson's, and 1 in 25, as based upon Mall's estimated prenatal mortality. But 

 even if, as estimated upon this basis, 4 or 10 per cent of all conceptions end in 

 hydatiform degeneration, this does not necessarily contradict the current opinion 

 regarding its rareness at or near term. 



A careful examination with the binocular microscope of all specimens has 

 shown that hydatiform degeneration as a rule is sufficiently general even in young 

 vesicles, so that sections of a single portion about 10 mm. square enable one to 



