CHAP, viii.] ORGANS OF RESPIRATION AND SECRETION. 249 



blood-vessels, and some muscular fibres. 



covering, and contains embedded vesicles 



It has an outer epithelial 

 of various sizes called 



Graafiati follicles containing the ova, or true female sexual 

 product. 



In the stroma of the ovary there is but little fibrous connective 

 tissue. It is made up mainly of large spindle-shaped cells,* which 

 surround the Gfraafian follicles, being arranged concentrically about 

 them. 



Upon dividing the ovary, vesicles of various sizes are seen within, 



Fig. 119. PORTION OF THE SECTION OF THE PREPARED CAT'S OVARY, REPRESENTED IN THE 



PRECEDING FIGURE, MORE HIGHLY MAGNIFIED. 



follicle, within which is situated the ovum 

 covered by the cells of the discus proligerus. 



8. A follicle further advanced. 



8'. Another which is irregularly compressed. 



9. The greater part of the largest follicle iu 



which the following parts are seen : a, 

 cells of the membrana granulosa lining the 

 follicle ; ft, the reflected portion, named 



1. Outer covering of the ovaiy. 



'2. Fibroiis stroma. 



:5. Superficial layer of fibro-nuclear substance. 



.'}'. Deeper parts of the same. 



4. Blood-vessels 



5. Ovigenns forming a layer near the surface. 

 0. One or two of the ovigerms sinking deeper, 



and beginning to enlarge. 



7. One of the ovigerms further developed, now 

 enclosed by a prolongation of the fibrous I 

 stroma, and consisting of a small Graah'an ' 



discus proligerus ; c, vitellus or yelk part of 

 the ovum, surrounded by the zona pellucida ; 

 d, germinal vesicle ; e, germinal spot. 



and these are much more numerous in the very young animal than 

 in the adult. 



These vesicles, or " Graafian follicles," are naturally spherical or 

 oval, and have three coats. The first and most external of these, 

 the tunic of the ovisac, or tunica fibrosa, is a fibrous, vascular 

 membrane, containing oval nuclei, but destitute of oil globules. 

 The second coat is the ovisac, formed of connective tissue, rounded 

 cells, and minute oil globules. The third coat (if it should ^be 

 really recognized as distinct) is the membrana granulosa, consisting 



See Klein and Noble Smith's Atlas of Histology. 



