ORIGIN OF THE CORPUS LUTEUM 179 



The specimens have nearly all been obtained at operation upon 

 gynecological patients, who before operation are usually sub- 

 jected to palpatory examinations, often none too gentle. Any 

 gynecologist will know that the rupture of a 'small ovarian 

 cyst' by the examiner's hands is a not infrequent occurrence; 

 such cysts, were they actually large follicles, immature or in 

 early atresia, if removed a day or two after the artificial rup- 

 ture, might present the anatomist with all too convincing speci- 

 mens of 'early corpora lutea.' Other possibilities of error might 

 be suggested, none of which can be ruled out until the ova are 

 studied with the specimen. While awaiting that almost impos- 

 sible outcome, we shall be wise to follow those workers with the 

 human corpus luteum whose findings are most nearly confirmed 

 by the evidence of comparative anatomy. 



The interpretation of the origin and morphology of the corpus 

 luteum given in these pages does not represent a wide diver- 

 gence from previous views. Nearly all observers now agree in 

 describing the persistence of the membrana granulosa and its 

 invasion by elements arising in the theca interna. The present 

 work, so far as it traces the fate of the theca cells, is in accord 

 with the best of recent investigations, and the author's hy- 

 pothesis of the persistence of all the theca cells as distinct ele- 

 ments would, if finally proved, explain the remaining difficulties. 



It is not so easy to align the findings in the sow's corpus luteum 

 with the conceptions of Sobotta and his followers, who believe 

 that the theca interna cells revert to mesoblastic type and by 

 division give rise to a strain of fibroblasts which lay down the 

 connective-tissue frame of the corpus luteum. This view implies 

 a notion of the structure of the adult corpus which differs from 

 that found in swine, and will necessitate a new study of the cell 

 types and the relation of the reticular fibrils to fixed cells in 

 corpora lutea of animals such as the mouse and sheep before 

 the discrepancy can be understood. 



In conclusion, it is a pleasure to express my thanks to Professor 

 Evans for his encouragement and generous provision of aid and 

 materials for this work. 



