166 GEORGE W. CORNER 



of lipoid granules, the latter considerable amounts. But now 

 the membrana propria is done away with, the granulosa cells 

 have increased in size and are becoming rich in lipoids, while the 

 theca interna cells are losing their lipoids. It is not strange 

 that investigators have become involved in uncertainty regarding 

 the further fate of the theca cells. I have seen the abrupt end- 

 ing, at stages similar to those now being described, of two careful 

 attempts, by students in our histological courses, to follow the 

 theca cells of the mouse and rat by means of their osmium- 

 staining inclusions, owing to failure to observe further distinc- 

 tions between the two cell types. In the pig, however, we pos- 

 sess a peculiar advantage in the tendency of the phosphatid 

 material to form the previously mentioned cytoplasmic rings 

 when fixed with slow aqueous fixatives, giving the granulosa 

 cells a distinctive appearance. There are other less regularly 

 present criteria, which when added together afford the prac- 

 ticed observer means of partially distinguishing the two cell 

 types; these are a tendency of the cytoplasm of the theca cells 

 to take acid stains somewhat more deeply than the granulosa 

 cells (perhaps this indicates merely a denser cytoplasm) and also 

 the regularity in size and closely packed disposition of the lipoid 

 granules or the vacuoles left when they disappear or are dissolved. 

 Following these clues, we find that many of the theca interna 

 cells remain in their original location about the periphery of the 

 follicle, running into the interior of the folds produced by the 

 collapse; but also that many of them, as the blood-vessels grow 

 inward, are carried or wander with the vessels, and become dis- 

 seminated among the cells of the membrana granulosa, where 

 they are finally lodged, either singly or in small groups, fre- 

 quently along the capillaries (fig. 18). It must be remembered 

 that a general scattering of the theca cells among the granulosa 

 in this way will not require a longer journey for any single cell 

 than the thickness of the inner layer, which is not more than 

 0.2 mm. The cells thus immigrating resemble in every way their 

 mates left behind at the periphery and in the folds, some of 

 them containing large granules, staining black with osmium 

 tetroxide, others showing almost no fatty inclusions (fig. 19). 



