CORPUS LUTEUM IN OVARY OF THE CHICKEN 5 



different parts of the ovary, mostly in the thcca interna, while 

 the interstitial cells he in the general stroma, and especially on 

 the periphery. 



Figure 3 shows several very young oocytes from the same 

 ovary as figure 1. In these, the follicle consists only of a single 

 layer of epithelial or granulosa cells (g). The connective tissue 

 layers are not yet formed. But there are nests of clear cells (I) 

 in the stroma nearby. Presumably these are included with the 

 connective tissue when the theca interna is formed. 



III. DISCHARGED FOLLICLES OF THE HEN'S OVARY 



In the largest follicles before ovulation, the three layers are 

 stretched out very thin by the pressure of the large yolk within 

 them. After o^oilation, there is a shrinkage of the follicle walls, 

 probably due to the elasticity of the connective tissue recoil- 

 ing at the sudden release of pressure from inside. On the Barred 

 Plymouth Rock ovary, the ripe yolk measured about 40 mm. in 

 diameter, and the last discharged follicle measured 20 mm. in 

 length from base to tip, while the next to last was 12 mm., 

 and the fourth in the series was 7 mm. As this shrinkage in 

 length takes place, the walls thicken until finally a small oval 

 mass results having no resemblance to a hollow follicle. The 

 ruptured place through which ovulation took place, becomes 

 gradually closed up, by the growing together of the edges, and 

 the filling of cells into the cavity. Sometimes this mass of cells 

 proti-udes shghtly from the cavity at the old place of rupture, 

 thus somewhat more resembling a miniature mammalian corpus 

 luteum. Yellow pigment forms in the puckered edges of the 

 follicle and also in the central mass. 



The microscopic study of sections through discharged follicles 

 of various ages shows that the increase of thickness of walls is 

 due chiefly to a thickening of the theca interna. Figure 4 is a 

 section of the last discharged follicle of the Barred Plymouth 

 Rock ovary. It shows the thickened theca interna (i) and in 

 addition the remnants of the granulosa (g). The latter seems 

 to loosen from the follicle after ovulation, and the cells collect 

 in masses in the cavity and degenerate. 



