PROCESS OF OVULATION AND FORMATION OF CORPORA LUTEA. 203 



when impregnation has been effected, only after two or three 

 months. It then appears as a mass occupying the previous 

 position of the follicle, but exceeding it in size, and divisible 

 into a central, usually red, but subsequently clear grey-coloured 

 part, and an intensely yellow and plaited peripheral portion 

 that is invested externally by what was formerly the tunica 

 fibrosa of the follicle. In a recent corpus luteum the middle 

 portion contains vascular connective tissue resembling mucous 

 tissue, and numerous large cells filled with granular red colour- 

 ing matter and crystals of hsematoidin (see Zwicky, 129, and Vir- 

 chow, 120). The peripheral zone is composed of two kinds of 

 cellular elements ; those that are situated most internally are 

 large, polygonal, pale, and finely granulated cells that, as may 

 easily be perceived in the Rabbit, proceed from the epithelium 

 of the follicle ; between these, vascular highly cellular processes 

 everywhere extend, both from the periphery and from the 

 centre, which give rise to the folding of the yellow zone. 

 However abundantly the epithelial portion of the corpus luteum 

 is developed in the first instance, it seems at a later period to 

 disappear almost completely, a small residue of this voluminous 

 structure alone remaining in the form of a white cicatrix the 

 corpus albicans. The cause of the retrogressive degeneration 

 of the corpus luteum is referred by His (52) to an atrophy of 

 the arteries, that are here provided with very thick walls. It 

 is remarkable that with incipient pregnancy the corpora lutea, 

 which are then distinguished as the corpora lutea vera, are 

 developed to a much greater extent, and remain to the end of 

 gestation, whilst the corpora lutea spuria disappear in the 

 course of a few weeks. This seems to speak in favour of an 

 additional purpose fulfilled by the corpora lutea, namely, to 

 cover, as Pfliiger (84) has pointed out, the loss of substance 

 occasioned by the evacuation of the Graafian follicles. 



We are indebted to His (52) for profound researches upon 

 the corpora lutea. I am, however, unable to coincide with his 

 view that the follicular epithelium does not participate in the 

 formation of the corpus luteum, notwithstanding that it is 

 entertained by Kolliker (59) and others ; but must side with 

 Schron (102), Pfliiger (84), and Luschka (72), who consider 

 that both elements of the follicular wall contribute to its forma- 



