THE SEXUAL ORGANS. 



267 



Fig. 271. 



are composed at first of common formative cells, 0*005 — 0*009'" 

 in size, which afterwards pass, in part into fibres and vessels, 

 in part persist as cells, multiply 

 spontaneously, probably by division, 

 and serve for the formation of the 

 Graafian follicles. These, according 

 to Barry, at first appear as spherical fiy 

 agglomerations, 0*01 "'in size, of some 

 few cells, which contain in the in- 

 terior a clear vesicle — the germinal c- 

 vesicle ; but, by the formation of a & 

 delicate, structureless membrane on 

 the exterior, around the cells, which then represent an epithe- 

 lium, soon assume the nature of follicles. Very young Graafian 

 follicles of this kind (ovisacs, Barry) occur by thousands in the 

 ovaries of nearly mature embryos, and of new-born children, 

 in which the further development is very easily traced. Whilst 

 the follicle increases by the multiplication of the cells of its 

 epithelium (the membrana granulosa), and at the same time 

 acquires an external vascular, fibrous coat; a clear substance, in 

 Man containing but few granules, is collected in the interior, 

 detaching the germinal vesicle, 0*0065 — 0*008'" in size, with 

 a germinal spot of 0*001 — 0*0015'", from the epithelium, to 

 which at first it was closely applied, and forcing it into the 

 centre of the follicle. When this has attained the size of 

 0*02'", a membrane in close apposition with the membrana 

 granulosa, and surrounding the germinal vesicle and the whole 

 contents of the follicle — the vitelline membrane — becomes 

 evident; which is regarded by all authors as a secondary forma- 

 tion, although it probably exists, even in the very earliest 

 rudiment of the follicle, as an extremely delicate membrane, 

 closely surrounding the germinal vesicle. At first excessively 

 delicate, and scarcely perceptible, the vitelline membrane, when 

 the follicle has increased in size and contains more fluid, 

 becomes more distinct, owing to its removal from the wall of 

 the follicle, and rapidly thickens. In follicles of 0*04 — 005'", 



Fig. 271. Three Graafian follicles, from the ovary of a newly-born female child, 

 x 350 diam. 1, without; 2, with, acetic acid: a, structureless membrane of the 

 follicle ; b, epithelium {membrana granulosa) ; c, yelk ; d, germinal vesicle with spot ; 

 e, nucleus of the epithelial cells ; /, vitelline membrane, very delicate. 



