382 THE CORPUS LUTEUM OF iJASynii^S, 



between the follicles, whilst the larger are often f(jund at some 

 distance below the surface. With the formation of the corpora 

 lutea, most of these ova and follicles undergo degeneration, which 

 seems to affect them all except the 3'oungest near the surface, and 

 those which are nearing ripeness. The ova between and close to the 

 corporea lutea are the first to go, and the effect of the growing- 

 corpus luteum seems to make itself felt in ever widening circles, 

 so that tinalh', when the corporea lutea are fully formed, nearly 

 all the residual ova are atrophied, with the exception of those 

 3'oung ova immediately below the surface. A few of the larger 

 ova, further away from the influence of the corpus luteum, persist 

 for a little while longer, but ultimately the}^ atrophy and become 

 of no account. This change is a progressive one, and quickly 

 shows itself, so that when the corpus luteum has attained its full 

 development the ova, with the exception of the smallest and most 

 superficial, are in a state of atrophy (see fig. 17). 



The Atrophy of the Follicle, and the Corpus Luteum 

 Atreticum. 



In this place it will be fitting to describe the characteristics of 

 atrophic follicles and the so-called " corpora lutea atretica," that 

 is, the corpora lutea formed in connection with certain follicles 

 whose ova are not extruded. 



With regard to the atrophic or atresic follicle, it is found that 

 its fate is not the same in all cases. The difference depends on 

 the size and development of the follicle before its atrophy begins, 

 and upon the degree to which atrophic and other changes go on 

 in its component parts. 



The fate of the follicles near their ripeness will be described 

 later. The remaining unripe follicles may be roughly classified 

 into two varieties, large and small, whose characters have alreadj^ 

 been sufficiently described. In the larger follicles, up to about a 

 stage represented by fig. 4, the atrophic follicles may be divided 

 into those which ultimately come to have left one layer of cells 

 of the membrana granulosa, and those which have more than one 

 layer, two or three being a usual number. The atrophic process 



