860 GENERATION. 



The medullary portion of the ovary is exceedingly vascular and is composed of numer- 

 ous small bands, or trabecul* of connective tissue, with smooth muscular fibres. The 

 blood-vessels, which penetrate at the hilum, are large and convoluted, especially at the 

 hilum itself where there is a mass of convoluted veins, forming a sort of vascular bulb, 

 w hich has been described particularly by Eouget. In the medullary portion of the ovary, 

 which is sometimes called the vascular zone, the muscular fibres follow the vessels, m the 

 form of muscular sheaths. According to Rouget, the mass of vessels at the hilum con- 

 stitutes a true erectile organ. 



In addition to the blood-vessels, the ovary receives nerves from the spermatic plexus 

 of the sympathetic, the exact mode of termination of which has not been ascertained. 

 Lymphatics have also been demonstrated at the hilum. 



Graafian Follicles. These vesicles, or follicles, were described and figured by De 

 Graaf and are known by his name. They contain the ova. undergo a series of interest- 

 ing changes, enlarge, approach the surface of the ovary, and finally are ruptured, dis- 

 charging their contents into the fimbriated extremity of the Fallopian tube. 



It was formerly supposed that the smallest Graafian follicles were situated deeply in 

 the medullary portion of the ovaries, approaching the surface gradually, as they became 

 larger; but it is now known that they are developed exclusively in the cortical substance. 

 If, indeed, we examine the ovary at any period of life, we find no follicles properly in the 

 medullary substance; but a few of the larger may project downward, so as to encroach 

 somewhat upon it, being actually of a diameter greater than the thickness of the cortex. 



The earlier anatomists supposed that the Graafian follicles were few in number, fifteen 

 or twenty, but they counted those only that were readily seen with the naked eye. When, 

 however, it was calculated that ova might be discharged every month during a period of 

 about forty years, it became evident that the follicles must either be quite numerous or 

 become successively and constantly developed. This led some anatomists, who believed 

 that, at the age of puberty, the ovaries contained, either partially or fully developed, all 

 the follicles that ever existed in these organs, to increase their estimates of the number 

 of follicles. Sappey, from a series of careful observations on this point, puts the number 

 of follicles at from 600,000 to 700,000. We cannot but regard this estimate as very much 

 exaggerated. According to the table of measurements given by Waldeyer, the primor- 

 dial follicles in the human embryo, at the seventh month, measure from ^ to ^ of an 

 inch, and the primordial ova, from T1 ^ to j^Vo of an m ch. From what has been written 

 on this point, it seems difficult, if not impossible, to give an approximation, even, of the 

 number of follicles in the ovaries, but there certainly must be several thousands, many 

 of which may never become fully developed. 



Within the last few years, very important advances have been made in our knowledge 

 of the mode of development of the ova and ovaries, which will be more fully considered 

 hereafter; but we must here refer to these points briefly, in order to give a clear idea of 

 the relations of the Graafian follicles, in the different forms which they present under 

 varied conditions of development. 



The ovary appears, particularly from observations upon the development of the chick, 



ery early in embryonic life, in the form of a cellular outgrowth from the Wolffian body. 



ts cells are small, but, as early as the fourth or fifth day, some of them are to be 



ished by their large size, their rounded form, and the presence of a large nucleus. 



Is are supposed to be primordial ova. In the process of development of the 



wy, some of the peripheral cells penetrate in the form of tubes (the so-called ova- 



s) and, at the same time, delicate processes, formed of connective tissue and 



essels extend from the fibrous stroma underlying the epithelium and enclose col- 



: cells. It is probable that we have these two modes of formation of follicles ; 



md J %** V^ f e P ithelial tabes from the surface, which become constricted 



r into closed cavities, and the other, by the extension of fibrous processes 



