ORIGIN OF THE CORPUS LUTEUM 



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the large size of the discus proligerus (as large as the entire 

 follicle of the mouse) places the ovum at such a distance from the 

 vascular bed that special vessels are needed for its nutriment. 



Be this as it may, by the time maturation of the ovum is in 

 progress, the character of the discus proligerus has become con- 

 siderably modified (fig. 7). Its cells are very much swollen by a 



Fig. 7 Portion of wall of mature Graafian follicle (sow in heat), showing 

 mature ovum in situ, and discus proligerus in process of dissociation. X 50. 



vacuolization of the cytoplasm, so that they stand farther apart 

 from each other, and in many places seem to be no longer in 

 contact. About the ovum the cells of the corona radiata still 

 hold together, but the rest of the discus has nearly crumbled 

 away, and the slightest disturbance must complete the freeing 

 of the ovum, bound as it now is to the parietal granulosa only 



