478 



THE OVARIES. 



The zona peUucula of the mature ovarian ovum, when viewed "with a 

 low magnifying power, appears clear or homogeneous, but according to 

 some observers, when sufficiently magnified, it presents an appearance 

 of minute radial striation, which has been considered to indicate in it 

 the existence of a porous structure, somewhat of the same nature as 

 that which is very obvious in the viteUine membrane of fishes and some 

 other animals. 



Through this membrane, as has been proved by observations in 

 several mammiferous animals, the spermatic filaments pass in order 

 to effect fecundation ; but it is difficult to comprehend how they are 

 transmitted, as no micropyle, or other aperture of sufficient size, has 

 3'et been detected in the zona of man or Mammals. 



Fiff. 



539. — Thin Transverse Section op the Ovary op a Newly Born Child 

 Highly magnified (Waldeyer). 



a, Ovarian or germinal epithelium ; h, formation of an ovarian tube ; c, c, ovigerms 

 lying in the germ-epithelium ; d, d, longer tube forming follicles (according to Pfluger's 

 and Waldeyer's views) ; e, c, germ -spherules forming ova and follicles ; /, earliest dis- 

 tinctly formed follicle with ovum and granular cells ; (/, g, blood-vessels. 



The germinal vesicle with its nucleus or macula belongs to the 

 ovum only, while it is still within tlie Graafian follicle. At the time of 

 complete maturation of the ovum, and even for a short time previous to 

 the bursting of the wall of the follicle by which the ovum escapes, 

 the germinal vesicle already begins to become flaccid and eollapfee, 

 and when the ovum has escaped from the follicle, the vesicle is no 

 longer to be perceived in the mass of granular protoplasm which con- 

 stitutes its germinal part. 



rormation of the Ovum and Graafian follicle. —The mode of origin of 

 tlie ova and Graafian follicles will be described under Development. As con- 

 nected, however, with the structure of the ovary in relation to the ova and 

 their origin, it Is proper to refer at this place to the view first suggested by 



