468 DEVELOPMENT OF THE GRAAFIAN FOLLICLES, [sect. 2o8. 



Such Graafian follicles (ovisacs, Barry) are found in thousands in 

 the ovaries of the nearly mature foetus and of the newly -born infant, 

 and their subsequent development is very easily followed. The 

 follicle grows by the multiplication of the cells of its epithelium 

 (i.e. of the membrana granulosa), and at the same time a fibrous 

 vascular envelope is formed upon it from without ; meanwhile, a 

 clear substance (in man, having but few granules), collects in the 

 interior, and pushes the germinal vesicle (o - oo65" to o - oo8'" in 

 diameter), with its germinal spot (cyooi'" to o - ooi5"'), from the 

 epithelium, to which it was at first closely applied, into the mid- 

 dle of the follicle. When the Graafian follicle has attained a 

 diameter of C02'", another envelope appears in its interior, en- 

 closing the germinal vesicle and the entire contents of the follicle, 

 and lying closely upon the membrana granulosa. This is the 

 vitelline membrane, which all authors regard as a secondary for- 

 mation, although, perhaps, it is present even in the very earliest 

 rudiment of the follicle, as an extremely fine membrane, closely 

 surrounding the germinal vesicle. At all events, when first 

 traceable, the vitelline membrane is extremely delicate and scarcely 

 perceptible, but subsequently becomes more distinct as the follicle 

 becomes further enlarged and acquires new fluid ; for now it gets 

 l- moved from the wall of the follicle, and shortly also becomes 

 thickened. In follicles of cro.4/" to crc^'" in diameter, the ovula 

 are already perfectly distinct, and are disproportionately large, 

 being surrounded with a delicate zona, -and still lying very near 

 to the walls of the follicles. The further development can be 

 easily understood ; and I will only remark further, that' it is but 

 rare to find follicles visible to the naked eye in newly-born infants ; 

 on the other hand, such follicles make their appearance even be- 

 fore puberty, but not until this period do they begin to show 

 themselves conspicuously. 



According to what has been said, the mode of origin of the 

 Graafian follicles belongs to the same category as that of the 

 tubular glands. The first commencement is a heap of Cells, at first, 

 perhaps, without any cavity or contents, and then arises the struc- 

 tureless membrane, not by the coalescence of the outermost cells, 

 but probably as a secretion from them; thus a follicle is formed, 

 which therefore corresponds in all respects to a shut gland vesicle, 

 or to a portion of a tubular gland canal. It is doubtful whence the 

 germinal vesicle and the vitelline membrane take their origin : the 

 whole ovum, Avith the germinal vesicle, is probably nothing else 

 than the central cell of the primitive rudiment of the Graafian 



