396 GYNECOLOGY 



While the proof of this is impossible, all a priori evidence is in its 

 favor. Those who attempt to overthrow the hypothesis certainly 

 undertake a heavy task in trying to establish an exception to the 

 uniformity of performance of one of the most complex and highly 

 specialized functions in the human body. The indication of the 

 genetic reaction is decidual transformation, and this is normally 

 found only in the mucosa of the corpus uteri, where indeed it occurs 

 in all cases of pregnancy, whether the latter be uterine or ectopic. 

 In certain cases we know that decidual changes may occur in other 

 portions of the Miillerian tract, most frequently in the Fallopian 

 tubes, a fact which probably helps to explain the occasional occur- 

 rence of pregnancy in the latter. 



With regard to ovarian gestation, in the specimens which have 

 been most fully studied, viz., those of von Tussenbroek, Thomp- 

 son, and myself, it is true that no definite decidual layer is found 

 in the wall of the gestation sac. Though von Tussenbroek, in her 

 first description, mentioned a decidual layer, she afterward stated 

 that this was an error, the cells being in reality lutein cells of the 

 corpus luteum. The final account is in the main correct, but she 

 cannot deny the possibility that some of the large cells were de- 

 cidual. However, admitting that no decidual cells are found in 

 specimens as advanced as those mentioned, we do not know that 

 they were not present at an earlier stage, when the ovum was very 

 small. One of the small ovarian decidual areas to which I have 

 referred would very soon disappear as a result of the outward 

 pressure of the expanding ovum, as well as of the phagocytic ac- 

 tion of the trophoblast, if there be no more tissue capable of un- 

 dergoing decidual changes, and it is quite evident that the ovarian 

 stroma proper does not tend to undergo this transformation. 



Even in tubal pregnancy, in which decidual changes are always 

 present in the early stages, there may be a marked disappear- 

 ance as pregnancy advances, the production of cells being evidently 

 much poorer than in the uterine mucosa in normal pregnancy, 

 though in the latter there is a considerable range of variation. In 

 my own recently described specimen of ovarian gestation I believe 

 that I have demonstrated a few scattered groups of decidual cells 

 in the ovarian stroma, near the inner wall of the gestation sac. 



For several years I have held the belief that decidual transform- 

 ation is peculiar to the Miillerian tract. The occasional finding 

 of the small areas of decidua-like cells in the ovary in uterine ges- 

 tation has been regarded by several writers as a proof that other 

 tissues may also undergo the change. From what I have already 

 stated it remains to be proved that these areas are not Miillerian 

 in origin. The occasional blending of Miillerian and ovarian tissues 

 has been abundantly proved, both by macroscopic and microscopic 



