THE SEXUAL ORGANS. 643 



inner finer plexus, "which extends as far as the membrana granulosa. 

 The veins arise in the same situation, arc in Man, for the most part, 

 very beautifully displayed in the walls of the larger follicles, and ter- 

 minate in the uterine and internal spermatic veins. A few lymphatic 

 vessels come out from the hilus ovarii, and proceed, in company with the 

 bloodvessels, to the lumbar, and pelvic glands. And with respect to 

 the nerves, they arise from the spermatic plexus, enter as minute trunks 

 with fine fibres, and " fibres of Remak," together with the arteries, 

 into the ovary ; but as respects their ultimate condition, they have not 

 yet been investigated. 



205. Detachment and re-formation of the ova, corpora lutea. 

 From the commencement of puberty up to. the period of involution, the 

 ovaries are the seat of a continual detachment of the ova by dchiscence 

 of the G-raafian vesicles, which, independently of sexual congress, takes 

 place in women and virgins, above all at the menstrual period, although 

 it may and does frequently occur at other times, under conditions not 

 yet accurately determined. In animals the same process is exhibited 

 at the time of "heat," although sexual congress appears to afford a 

 necessary impetus to its completion ; and in them the anatomical pro- 

 cesses may be more completely traced, whilst, in Man, the opportunity 

 for such observations is much more rarely afforded. 



When the Graafian follicles approach the time of bursting, they gra- 

 dually enlarge to a circumference of 4 to 6 lines and more, and are 

 continually brought more and more near to the surface, until they 

 project beyond it, as wartlike or hemispherical elevations, covered only 

 by a thin pellicle of the much attenuated t. albuginea, with its peritoneal 

 lamella. At the same time their vessels are remarkably multiplied, and 

 by the continual exudation from them, the liquor folliculi is rendered 

 more and more abundant, whilst the fibrous coat of the follicle, at the 

 bottom and sides, but not where the ovulum is situated, becomes thick- 

 ened towards the interior ; the membrana granulosa also swells a little, 

 and contains larger cells (up to 0-01 of a line.) When these processes 

 have advanced to a certain point, the thin, opposing coats can no longer 

 withstand the continued and ever-increasing pressure from the interior 

 of the follicle ; they give way at the most elevated, and most thinned 

 point, exactly where the ovulum is situated, and this body, surrounded 

 by the cells of the germinal eminence, if the oviduct has applied itself 

 exactly over the follicle, escapes into it. But the vital course of the 

 Graafian follicle is not hereupon concluded, for now a series of partly 

 new formations is presented in it, in consequence of which it at first 

 becomes a corpus luteum, as it is termed, and ultimately disappears 

 altogether. 



These corpora lutea are displayed in the most complete state, when 



