1905.] the Interstitial Cvllx of the Ovary in the Rabbit. 42 



of the peripheral ones. The rest of the cells which are not able, for one 

 cause or another, to undergo these changes, appear to remain quiescent for a 

 while, until finally they regress and pass into a condition of subserviency to 

 the needs of those which have become ova. Both follicle cells and inter- 

 stitial cells are, however, still potential ova. They have passed through the 

 initial stages, and only need enlargement and nuclear transformations in order 

 to become ova, should the appropriate stimulus be given. This chance is not 

 given to the follicle cells. As soon as the follicle begins to grow, they 

 multiply rapidly, and probably provide, by their disintegration, the follicular 

 secretion upon which the ovura feeds and grows. In the ripe follicle of the 

 rabbit there is almost complete disintegration of the membrana granulosa, and 

 the remains of the discus proligerus is presumably extruded with the ovum, 

 perhaps serving it as food material prior to its fertilisation, and subsequent 

 attachment to the uterine wall. The interstitial cells, however, have possi- 

 bilities before them, being still capable of carrying out any function belonging 

 to the true ovarian cell. 



All the true ovarian tissue is derived from the germinal epithelium, this 

 tissue forming in the adult rabbit by far the greatest part of the whole 

 ovary. There is relatively little mesoblast, which subserves solely the 

 function of support and of nutriment-carrier to the rest of the organ. We 

 may, therefore, look upon the whole ovary as consisting of two classes of 

 cells and of two only, namely, (1) those derived from the germinal epithelium 

 and performing all the ovarian functions, and (2) those derived from the 

 original mesoblast, which are supporting and vascular. 



There remains only one feature to be dealt with in the immature ovary, 

 one that has already been described by Balfour, namely, the protoplasmic 

 masses formed by the aggregations of young ova. In the ovary of the 

 sixteenth day the ova are all separate, but a day or two later this is not 

 the case. There are now a large number of these masses of various sizes. 

 They appear to consist of two, three, four, or even five young ova, to judge 

 by the number of nuclei seen, but it is impossible to distinguish any trace 

 of cell-boundary between them. Balfour suggests that these may either 

 form as many ova as there are nuclei, or that one ovum may develop at the 

 expense of the rest. This last point of view appears to be the more probable. 

 It is evident that the massing takes place subsequent to the formation of 

 the young ova, since it is not seen until after the appearance of the ova, 

 and it would appear rather purposeless if they merely separated again a 

 little later on. Moreover, in these masses one or two of the nuclei often 

 look as if they were disappearing by gradual dissolution, and it is, therefore, 

 probable that they will all ultimately serve as food-stuff for the one ovum 



