170 GEORGE W. CORNER 



small evenly packed vacuoles with a few tiny black granules 

 interspersed. 



In the substance of the corpus luteum are now found two types 

 of cells whose differing characteristics become well marked after 

 the beginning of the third week. One type is that whose iden- 

 tity with the granulosa is fully demonstrated by the presence 

 of the peculiar lipoid spherules about the periphery of the cyto- 

 plasm (figs. 2 and 21). From now on these cells grow slowly in 

 size, until just before delivery some of them have attained the 



'if 22 



immense size of 30 x 45^. During the first few weeks the neu- 

 tral fat increases until it greatly exceeds the small amount found 

 in the cells of the granulosa before rupture, and then grows pro- 

 gressively less, finally almost disappearing by the 110th day of 

 pregnancy. The phosphatid substance which produces the 

 artifacts of fixation, so frequently referred to, disappears also, 

 and therefore during the last third of pregnancy the cells, in 

 ordinary formol preparations, possess a homogeneous cyto- 

 plasm, strikingly different from the greatly vacuolated cell sub- 

 stance of the earlier stages (fig. 23). Just before delivery, 

 however, great globules of an osmium-staining material, pre- 

 sumably a fat, appear about the periphery of some of the cells. 



