HYDATIFORM DEGENERATION IN TUBAL AND UTERINE PREGNANCY. 345 



Yet, strange as it may seem at first sight, this is not a random guess but an estimate 

 based upon the actual incidence of hydatiform degeneration as determined by a 

 careful gross and microscopic examination of mounted and unmounted material 

 from over 400 abortuses. However, I lay no special emphasis on these percentages, 

 and am using them merely to emphasize the great frequency of hydatiform degenera- 

 tion. It matters little whether we shall ultimately determine an incidence of 10 

 or 5 per cent, but it does matter considerably whether we regard the frequency as 

 5 or 0.05 per cent, for this is a difference of 10,000 per cent. 



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

 prehensible 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 relatively 

 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 Mall 

 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 three months) would 

 lower it. But the result obtained would represent the incidence of hydatiform 

 degeneration 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 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 



