71 8 GENERATION AND DEVELOPMENT. 



mucous follicles are scattered beneath the mucous mem- 

 brane composing these parts of the external organs of 

 generation ; and at the side of the fore part of the vagina, 

 are two larger lobulated glands, named vulvo -vaginal, or 

 Duverney's glands, which are analogous 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. 



Un impregnated Ovum. 



If the structure and formation of the human ovary be 

 examined at any period between early infancy and ad- 

 vanced 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 al- 

 ready alluded to as the follicles or vesicles of De Graaf, the 

 anatomist who first accurately described them; they are 

 also sometimes called ovisacs. At their first formation, the 

 Graafian vesicles, according to Schron, are near the sur- 

 face 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 membranous envelope, composed of fine fibro- 

 cellular tissue, and connected with the surrounding stroma 

 of the ovary by networks of blood-vessels (fig. 208). This 

 envelope or tunic is lined with a layer of nucleated cells, 

 forming a kind of epithelium 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. 



