DISSECTION OF THE PELV] 



353 



The Graafian follicles vary greatly in size. The smallest are imbedded 

 in the cortical part of the ovary. These are of microscopic size, and 

 differ from the larger follicles in having only a single layer of cells in 

 the membrana granulosa, and in having no liquor folliculi. Follicles of 

 intermediate size are placed more deeply in the ovary, and differ from the 

 largest chiefly in the small amomit of liquor that they contain. These 

 differences of size represent different stages of development of the 

 follicles, the largest being the most mature. When mature, a follicle 

 occupies a considerable space in the substance of the ovary in the neigh- 

 bourhood of the hilus. Finally it bursts through the surface of the 



Fig. 45. 



Sl-ctiox of Cat's Ovary, magnified (from Schron). 



1. Outer covering of the ovary ; 2. Fibrous stroma ; 3. Superficial layer of fibro-nuclear substance; 

 3'. Deeper parts of the same ; 4. Blood-vessels ; 5. Ovi-sacs forming a layer near the surface ; 6. One 

 or two of the ovi-sacs sinking deeper and beginning to enlarge ; 7. One of the ovi-sacs farther 

 developed, now enclosed by a prolongation of the fibrous stroma, and consisting of a small Graafian 

 follicle, within which is situated the ovum covered by the cells of the discus proligerus ; 8. A follicle 

 farther advanced ; 8'. Another which is irregfularly compressed ; 9. the greater part of the largest 

 follicle, in which the following parts are seen ; a. Cells of the tunica granulosa lining the follicle ; 

 6. The reflected portion named discus proligerus ; c. Vitellus or yelk part of the ovum, surrounded 

 by the zona pellucida ; d. germinal vessicle ; e. Germinal spot. 



ovary, and the ovum, along with the liquor folliculi and part of the 

 membrana granulosa, escapes and is caught by the expanded extremity 

 of the Fallopian tube. The follicle then collapses, while it becomes in 

 part filled with blood from the vessels opened by the rupture of its wall. 

 The rupture then heals, and the follicle becomes converted into a 



2 A 



