THE UNIMPREGNATED OVUM. 563 



it, without a corpus spongiosum, and not perforated by the 

 urethra ; of two folds of mucous membrane, termed labia in- 

 terna, or nymphce; and, in front of these, of two other folds, 

 the labia externa, or pudenda, formed of the external integu- 

 ment, and lined internally by mucous membrane. Between 

 the nymphse and beneath the clitoris is an angular space, 

 termed the vestibule, at the centre of whose base is the 

 orifice of the meatus urinarius. Numerous mucous follicles 

 are scattered beneath the mucous membrane composing these 

 parts of the external organs of generation ; and at the side of 

 the fore part of the vagina, are two large lobulated glands, 

 named vulvo-vaginal, or Duverney's glands, which are anal- 

 ogous to Cowper's glands in the male. 



Having given this general outline of the several parts which, 

 in the female, contribute to the reproduction of the species, it 

 will now be necessary to examine successively the formation, 

 discharge, impregnation, and development of the ovum, to 

 which these several parts are subservient. 



Unimpregnated Ovum. 



If the structure and formation of the human ovary be ex- 

 amined at any period between early infancy and advanced 

 age, but especially during that period of life in which the power 

 of conception exists, it will be found to contain, on an average, 

 from fifteen to twenty small vesicles or membranous sacs of 

 various sizes; these have been already alluded to as the follicles 

 or vesicles of De Graaf, the anatomist who first accurately de- 

 scribed them ; they are also sometimes called ovisacs. At their 

 first formation, the Graafian vesicles, according to Schron, are 

 near the surface of the stroma of the ovary, but subsequently 

 become more deeply placed ; and again, as they increase in 

 size, make their way towards the surface. When mature, they 

 form little prominences on the exterior of the ovary, covered 

 only by the peritoneum. Each follicle has an external mem- 

 branous envelope, composed of fine fibro-cellular tissue, and 

 connected with the surrounding stroma of the ovary by net- 

 works of bloodvessels (Fig. 208). This envelope or tunic is 

 lined with a layer of nucleated cells, forming a kind of epi- 

 thelium or internal tunic, and named membrana granulosa. 

 The cavity of the follicle is filled with an albuminous fluid in 

 which microscopic granules float; and it contains also the ovum 

 or ovule. 



The ovum is a minute spherical body situated, in immature 

 follicles, near the centre ; but in those nearer maturity, in con- 

 tact with the membrana granulosa at that part of the follicle 



