158 GEORGE W. CORNER 



of endothelial nature, but at some few points, however, it is 

 impossible to convince oneself that the spindle-cells have any 

 connection with the vessels, for they are not always arranged in 

 tubular form and are sometimes well disseminated throughout 

 the granulosa in advance of any circulation of blood. It can- 

 not be denied absolutely, therefore, that some of them may be 

 inwandering cells of the perivascular spindle-cell zone of the 

 theca interna. During these early changes the large cells of the 

 theca interna remain in their place, and I have never seen con- 

 vincing evidence of their conversion into spindle cells. 



Practically all of those observers who have been convinced of 

 the persistence of the granulosa have described such an early 

 invasion of the innermost layer by spindle-cells, a stage which 

 was called by Robert Meyer the stage of proliferation, but as 

 in the pig there is doubt as to the interpretation of the observed 

 facts. Sobotta ('96) holds that all the cells of the theca interna 

 are converted into spindle-cells (fibroblasts), and wander into 

 the granulosa, dividing frequently, to form the connective-tissue 

 framework of the corpus luteum. In this view he is supported 

 by Marshall ('04) in his work on the sheep, and by O'Donoghue 

 ('16), who studied the marsupial ovary; but several authors, 

 including Volker ('05), Loeb ('06), and R. Meyer ('11), working, 

 respectively, with the corpora lutea of the marmot, the guinea- 

 pig, and man, are inclined to consider the first inwandering cells 

 as endothelial, and deny the conversion of the theca interna cells 

 into fibroblasts. 



It has been mentioned that the breaking-down of the raem- 

 brana propria and the invasion of the granulosa by spindle-cells 

 does not take place at once over the entire inner surface of the 

 collapsed follicle, but begins first at the apices of the folds, where 

 the structure has presumably been subjected to the greatest 

 mechanical strain. Because of this very important fact, we are 

 able to observe a definite stage at which, while in places there 

 is an actual intermingling of the two layers going on in part of 

 the structure (fig. 15 a, X), in other parts the two inner layers 

 of the wall maintain their original relations. During the same 

 period there is a marked and rather sudden change in the granu- 



