DEVELOPMENT OF THE GKAAFIAN FOLLICLE 405 



f tunica externa 



1. Theca folliculi -! tunica interna 



( membrana propria. 



2. Stratum (seu membrana) granule-sum. 



3. Liquor folliculi occupying the atrium folliculi. 



4. Discus proligerus. 



5. Corona radiata. 



6. Zona pellucida. 



7. Perivitelline space (possibly an artefact). 



8. Vitelline membrane. 



9. Vitellus. 



10. Nucleus or germinal vesicle. 



11. Nucleolus or germinal spot (if present). 



The Corpus Luteum. The rupture of the follicle is accom- 

 panied by sudden relief of the intrafollicular tension and conse- 

 quent hemorrhage from the thin-walled capillaries of the theca 

 folliculi. Thus the cavity of the follicle is filled with blood ; the 

 ruptured follicle is then known as a corpus hemorrhagicum. This 

 is the first stage in the formation of the corpus luteum. 



Promptly succeeding the formation of the corpus hemorrhagi- 

 cum, lutein cells appear at the periphery of the body. They are 

 large, ovoid or polyhedral cells having a clear finely granular cyto- 

 plasm and a peculiar yellow color due to the presence of a pigment 

 known as lutein. Moreover, the cytoplasm of the lutein cells 

 becomes very rapidly infiltrated with droplets of fat, likewise 

 deeply colored by the lutein pigment which is apparently held in 

 solution. The origin of these cells is somewhat obscure. By 

 certain observers they have been thought to result from the 

 growth and multiplication of those cells of the stratum granulosum 

 which remain after the rupture of the follicle (Bischoff, Pfliiger, 

 Sobotta) ; by others they are derived from the connective tissue 

 cells in the tunica interna of the theca folliculi (Kolliker, His, 

 Palladino). 



The lutein cells increase rapidly both in number and in size, 

 and gradually encroach upon the margin of the blood clot whose 

 progressive absorption precedes the advance of the lutein cells. 

 But not only does the lutein mass grow centralward, it also, and 

 especially in the event of fertilization of the discharged ovum with 

 the consequently increased vascularity of the reproductive organs, 

 grows at the periphery and in this way greatly increases the diame- 

 ter of the corpus luteum. 



