HYDATIFORM DEGENERATION IN UTERINE PREGNANCY. 205 



results. Like the fetuses which rarely accompany them, they are full-term or 

 near-term products when regarded as hydatiform degenerations, and unless we are 

 to assume that conceptuses once affected by hydatiform degeneration always survive 

 to near-term, statistical deductions based upon the cases that do survive can give 

 us little idea of the actual frequency of the condition throughout the entire period 

 of antenatal life. 



That the specimens upon which past and also present opinion is based usually 

 were large is confirmed by the belief in the prevailing clinical criterion of the 

 existence of a disproportionately large uterus in cases of hydatiform mole. The 

 emphasis laid on this by clinicians is well illustrated by Seitz (1904 b ), who said 

 that cases in which the uterus is too small are the exception. Indeed, it seems 

 that the validity of this clinical dictum has been questioned only very recently 

 by Briggs (1912). Since most early conceptuses showing hydatiform degeneration 

 have been inhibited in growth before being aborted, it probably is only the speci- 

 mens which continue to grow that produce a uterine enlargement greater than 

 could normally be expected. However, since, as emphasized by Gierse (1847), 

 Storch (1878), Hiess (1914), and others, most hydatiform moles are expelled early 

 and spontaneously, it is evident that these can not have been adherent that is, 

 have penetrated very deeply or they would not have been expelled early and 

 spontaneously. Furthermore, maceration changes so commonly present in 

 aborted hydatiform moles indicate very clearly that a large percentage of them, 

 together with the decidua, had been more or less completely detached from the 

 uterine wall some time before abortion occurred. 



As far as one can gather from the literature, the present opinion regarding the 

 incidence of hydatiform degeneration would be paralleled quite correctly if, in the 

 case of measles, we assumed that it was as common in octogenarians as in children. 

 Measles, indeed, is an extremely rare disease in advanced age, but it nevertheless 

 is very common in infancy. This is exactly the mistake we have made regarding 

 hydatiform degeneration. It may be and undoubtedly is a rare disease at or near 

 term, as Gierse also stated, but it probably is the commonest of all diseases during 

 the earliest months of gestation. The typical large hydatiform mole is an end- 

 result which it has taken long months to develop. No one seems to have followed 

 its evolution, although hydatiform degeneration, whether total or partial, is, of 

 course, gradual in its advent. 



The records of the Carnegie Collection contained 8 cases of hydatiform mole in 

 the first 2,400 accessions, showing a frequency eight times as great as that given by 

 Williamson, or an excess of 700 per cent. Since the first 2,400 accessions contain 

 309 cases of tubal and 2 of ovarian pregnancy, only 2,089 uterine specimens 

 remain. Hence the recorded incidence in the uterine specimens really is 8 in 2,089, 

 or 1 in every 261 cases. This incidence is only slightly lower than that of Kroemer, 

 and somewhat higher per 1,000 than that given by Essen-Moller for the Frauen- 

 klinik at Lund, or than the personal experience of Cortiguera. 



The highest incidence of hydatiform degeneration previously reported is that 

 of Storch, who estimated it as 50 per cent, but he unfortunately did not give a 



