5° 



OBSTETRICAL ANATOMY. 



in its short diameter. Tlie texture of the ovaries is also liable to various 

 abnormal alterations. 



The Graafian vesicles are present in the ovary of the foetus, but they do 

 not attain their full development until puberty ; neither are they all present 



at birth, but are continually being devel- 

 oped beneath the tunica albuginea. The 

 first-formed elements in the foetal ovary 

 are cells and cell-nuclei ; these next ap- 

 pear in somewhat circular groups, which 

 are more opaque than the other parrs of 

 the regularly uniform mass (Fig 24, A). 

 A kind of film soon condenses round 

 these groups (B), and upon the inner 

 surface of this there is fixed an epithelial 

 precipitate from the fluid and granules of 

 ihe interspaces of the contained primary 

 cells. Within the ovisac thus formed, 

 a large nucleate cell becomes visible : this 

 is the commencement of the ovum (C, g). 

 As this expands, the proportion of fluid 

 to the formified particles increases, and 

 the latter are attracted to the contiguous 

 surfaces : some to that of the ovisac, 

 which thus becomes lined by a thicker 

 layer of cells ; others to the ovum, ac- 

 cumulating around it. With the enlarge- 

 ment of the ovisac, the stroma of the 

 ovum condenses around its delicate 

 membrane (Fig, 25, h), to form what has 

 been called the " theca folliculi " of Baer 

 — the fibrous tunic already noted ; this 

 vascular tunic {a), with the other {b), 

 constituting the vesicle ; while the stratum 

 of nucleate cells lining this double cover- 

 ing is the membrana granulosa, and those 

 surrounding the ovum itself form the/r<?- 

 Hgerous disc (e), the mass of cells adhering 

 thereto being the ciwiulus. 



The hyalinion, or proper tunic of the 

 ovum, thickens into the clear substance 

 improperly named the zotia pellucida (/), which in reality is a bag. As 

 the cells and cell-nuclei of the ovum become developed, they are pushed 

 deeper into the stroma by those of more recent formation ; while, as the 

 ovum ripens, the cells immediately around it become elongated and pyri- 

 form, the tapering extremity being attached to the zona : those of the 

 cumulus diverge irregularly into the fluid intervening between them and 

 the membrana granulosa of the ovisac. What have been termed reiina- 

 culce id) have been described by some authorities ; they are four processes 

 formed by the cells of the cumulus, and may be merely exceptional diver- 

 gences. 



Until puberty there is no great activity apparent in the vesicles ; but at 

 this time the ovary becomes more vascular, and certain vesicles increase 

 in volume. At the period of " rut " or " heat," one or more vesicles, 



Fig 24. 



Formation of the Ovisac in the 



Bitch's Ovary. 



