ORIGIN OF THE CORPUS LUTEUM 161 



still intact; in these areas we find that it is the granulosa cells 

 alone which have assumed the appearance of the large cells of 

 the corpus luteum, commonly called lutein cells. 



The breaking-down of the membrana is followed by a rapid 

 sprouting and branching of the blood-capillaries throughout the 

 entire granulosa (figs. 16 and 17). This stage is represented, in 

 my material, by seven sows, of which one contained fertilized 

 ova (some unsegmented and some with two blastomeres) ; one 

 was killed about five days after the onset of heat, no ova being 

 found, probably having degenerated; one was killed about six 

 days after the onset of heat, one degenerate ovum being found; 

 the other four were among those received from the University 

 Farm School, in which the ova were not sought, but in which the 

 dates of copulation were accurately known, in two on the third 

 day and in two on the fifth day before killing. 



Coincidently with the spread of the blood-vessels in a network 

 throughout the granulosa, there continues a marked swelling of 

 the cells of this layer, which double or more than double in 

 diameter, thus making an eightfold increase in volume; some of 

 them reach dimensions of 30V to 35^- The nuclei are larger 

 and more vesicular. I have never seen a mitotic figure in a 

 cell of the granulosa at this or later stages, and feel sure that the 

 generalization of Sobotta on this point is correct. In the 

 formol- or Bouin-fixed specimens, the periphery of the cells is 

 studded with the striking ringlike phosphatid artifacts of fixation 

 (fig. 18, gr.l.c). The rest of the cytoplasm is thin and contains 

 irregular vacuolar spaces, due partly perhaps to the shrinking 

 away, during fixation, of the cell-substances which form the ring 

 bodies, and partly to the solution in the alcohols, xylol, or ether, 

 of other lipoid substances, which osmic preparations show as 

 small black globules in the center of each ring and also scattered 

 about the nucleus or throughout the cytoplasm. I have not 

 been able to apply other microchemical tests to the tissues at 

 this stage, but the globules are morphologically like the neutral 

 fat of later stages (fig. 3), and I assume that they are indeed 

 the neutral fat or its forerunner. 



