6 RAYMOND PEARL AND ALICE M. BORING 



The first subsequent discharged folHcle in the series to show 

 any new microscopic features is the sixth (fig. 5), where there 

 appears a marked increase in the number of nests of vacuo- 

 lated cells in the theca interna (l). They are concentrated 

 toward the cavity. The closeness of nests together may be 

 partlj^ due to the shrinkage of the cavity after discharge of 

 the egg. But as this does not seem sufficient to account en- 

 tirely for the increase, the number must be added to either by 

 di\dsion or migration. The fact that division plays some part 

 in the process is proven by the observation of several mitotic 

 spindles. The character of these cells shows better in greater 

 magnification, as in figure 6 and figure B. 



The further progress of the increase of vacuolated cells in the 

 theca interna is shown in figure 7, a section of a discharged fol- 

 licle too small to have been placed in the series as to time of 

 discharge. Here the whole internal theca looks full of holes, 

 due to vacuolated cells (I). The central ca\dty is nearly oblit- 

 erated, almost as though the edges had been pulled up by a 

 gathering string. There are, however, a few cells in the central 

 cavity (p). These get in there by migi-ation from the internal 

 theca. 



Figure 13 shows the process in an atretic follicle where it is 

 more conspicuous, but it is true to a more limited extent in the 

 discharged follicles. The cells concerned have a speckled ap- 

 pearance in figiue 13 (d). They are abundant in the follicle 

 wall, some are scattered among the yolk spheres in the central 

 cavity and some are on the border line between the follicle wall 

 and the cavity, indicating that the cells actually migrate into 

 the cavity. Occasionally a very large central plug is formed 

 which protrudes from the spot of rupture. Figure 7 shows a 

 small plug of this kind (p). 



The cavity usually becomes finally obhterated by the thick- 

 ening of the internal theca and the formation of large masses 

 of vacuolated cells from the original nests. In figure 8, the 

 chief tissue consists of the masses in the internal theca (i). The 

 line between the theca interna and externa is marked by the 

 irregular spaces and blood vessels. The connective tissue in the 



