PROBLEMS IN OBSTETRICS AND GYNECOLOGY 395 



from blood which had been effused into the cavity of the follicle. 

 The explanation of these irregular phenomena is quite uncertain, 

 and is deserving of careful investigation. 



Another interesting histologic appearance has been described 

 in recent years by Pels Leusden, Schmorl, and others, viz., small 

 localized areas of decidua-like cells in the ovary in some cases of 

 uterine pregnancy. I have recently examined ten specimens in 

 my museum, and have found these changes in four ovaries. In 

 one a single area was found in a complete section of the ovary; in 

 the others, two were found at different portions and varying in 

 size. In each instance the areas were situated in the cortex, at or 

 near the surface, sometimes projecting slightly from the latter, 

 sometimes extending some distance into the cortex. The cells in 

 these areas bear the closest resemblance to the uterine decidua in 

 normal pregnancy, presenting similar variations in size and shape. 

 The line of demarkation from the surrounding ovarian stroma is 

 always well marked, giving the impression that the two tissues 

 are distinct. Usually these areas contain dilated capillaries which 

 are not found in the neighboring unchanged ovarian stroma. 



I have never found such areas in ovaries removed from non- 

 pregnant women. What is the explanation of these changes? It 

 might be suggested that they are peripheral portions of the theca 

 interna of the ripening Graafian follicles or of a corpus luteum. Serial 

 sections show, however, that this is not the case. The large cells 

 are undoubtedly of connective-tissue origin, but their definite lo- 

 calization suggests some special characteristic which makes the 

 cell capable of undergoing the same genetic reaction which is or- 

 dinarily found in the uterine and tubal mucous membrane when 

 pregnancy develops in relation to these tissues. 



Tentatively, I advance the view that these areas represent dis- 

 placed portions of Miillerian tissue, which have become attached 

 to the surface of the ovary in early embryonic life. Occasionally, 

 I have found in the substance of such an area a gland-like space 

 lined with columnar or cubical epithelium. The latter may, of 

 course, be simply a derivative of the surface germinal epithelium, 

 but it may indeed represent included Miillerian epithelium. 



It is possible that the special genetic reaction in these areas may 

 sometimes determine the imbedding and development of a fertil- 

 ized ovum in the ovary, and if the opinion that they are Miillerian 

 in origin be correct, it is not unlikely that all cases of pregnancy 

 in ovarian tissue may still serve to support the dictum which has 

 been widely believed in recent years, viz., that imbedding and devel- 

 opment of the fertilized human ovum in the earliest stages can 

 only take place in a tissue capable of undergoing a special genetic 

 reaction, and that this tissue is in all cases Miillerian in origin. 



