768 GENERATION. 



After the peritoneum has reached the ovary, its fibrous layer becomes 

 indistinct and fuses with the fibrous stroma of the ovary itself. The peri- 

 toneal endothelium here undergoes a change, and the cells covering the 

 ovary are cylindrical. This change in the structure of the peritoneum is 

 abrupt and is indicated by a distinct line surrounding the hilum of the 

 ovary. There seems to be little difference between the epithelial cells cov- 

 ering the ovaries and those lining the Fallopian tubes, except that the 

 latter are provided with cilia. 



On making a section of the ovary, it is readily seen by the naked eye that 

 the organ is composed of two distinct structures ; a cortical substance, for- 

 merly called the tunica albuginea, which is about Y V ^ an i nc ^ (1 mm -) in 

 thickness, and a medullary substance containing a large number of blood- 

 vessels. The cortical substance alone contains the G-raafian follicles. The 

 external layer of this is denser than the deeper portion, but there is no 

 distinct fibrous membrane such as is sometimes described under the name of 

 the tunica albuginea. 



The cortical substance of the ovary consists of connective tissue in sev- 

 eral layers, the fibres of which are continuous with the looser fibres of the 

 medullary portion. In the substance of this layer, are embedded the ova, 

 enclosed in the sacs called Graafian follicles. This layer contains a few 

 blood-vessels, coming from the medullary portion, which surround the fol- 

 licles. 



The medullary portion of the ovary is very vascular and is composed of 

 small bands, or trabeculae of connective tissue, with non-striated muscular 

 fibres. The blood-vessels, which penetrate at the hilum, are large and con- 

 voluted, especially at the hilum itself, where there is a mass of convoluted 

 veins, forming a sort of vascular bulb (Rouget). In the medullary portion 

 of the ovary, which is sometimes called the vascular zone, the muscular fibres 

 follow the vessels, in the form of muscular sheaths. 



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

 matic 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 DeGraaf, in 1672, and are known by his name. They contain the ova, 

 undergo a series of peculiar changes, enlarge, approach the surface of the 

 ovary, and finally are ruptured, discharging their contents into the fimbriated 

 extremity of the Fallopian tube. The Graafian follicles are developed ex- 

 clusively in the cortical substance. If the ovary be examined at any period 

 of life, no follicles are found 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 entire 

 number of follicles of all sizes in each ovary is about 36,000 (Henle). Ac- 

 cording to the table of measurements given by Waldeyer, the primordial fol- 

 licles in the human embryon, at the seventh month, measure -gfa to *icr of 

 an inch (30 to 100 /A) in diameter, and the primordial ova, y^r to TffW of 

 an inch (15 to 25 /A). 



