636 HANDBOOK OF PHYSIOLOGY. 



(the ligament of the ovary), and, more slightly, to the Fallopian tubes 

 by one of the fimbriae into which the walls of the extremity of the tube 

 expand. 



Structure. The ovary is enveloped by a capsule of dense fibro-cellu- 

 lar tissue, called the tunica albuginea, covered on the outside by epithe- 

 lium (germ-epithelium),- the cells of which, although continuous with, 

 and originally derived from, the squamous epithelium of the peritoneum, 

 are short columnar (A, Fig. 426). 



The internal structure of the organ consists of a peculiar soft fibrous 1 

 tissue a kind of undeveloped connective tissue, with long nuclei closely 

 resembling unstriped muscle (C, Fig. 426) or stroma, abundantly sup- 

 plied with blood-vessels, and having imbedded in it, in various stages of 

 development, 'numerous minute follicles or vesicles, the Graafian vesi- 

 cles, or sacculi, containing the ova (Fig. 426). 



If the 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 a number of these vesi- 

 cles. Immediately under the tunica albuginea (Fig. 426) they are small 

 and numerous, either arranged as a continuous layer, as in the cat or 

 rabbit, or in groups, as in the human ovary. These small follicles im- 

 bedded in the soft stroma of fine connective tissue and unstriped muscle- 

 form here the cortical layer; they are sometimes called ovisacs. 



Each of the small follicles of this layer has an external membranous 

 envelope, or membrana propria. This envelope or tunic is lined with a- 

 layer of nucleated cells, forming a kind of epithelium or internal tunic, 

 and named the membrana granulosa. The cavity of the follicle is filled 

 up by a nucleated mass of protoplasm enclosed in a very delicate mem- 

 brane, which is the Ovum. The nucleus contains one or more nucleoli. 

 The nucleus is known as the germinal vesicle, and the nucleolus as the 

 germinal spot. 



The central portion of the stroma of the ovary extends from the cor- 

 tical layer to the hilum of the organ, at which enter the numerous arte- 

 ries, fibrous tissue, and unstriped muscle, forming a highly vascular 

 zona vasculosa. Within this central zone are contained the fully-devel- 

 oped Graafian follicles, varying in size, however, but considerably larger 

 than those of the cortical layer. In these follicles the cavity is not nearly 

 filled by the ovum, which is attached at one side to the zona granulosa 

 by a collection of small cells, the discus proligerus, the remainder of the 

 cavity being filled with fluid. The envelope of the ovum, or zona pellu- 

 cida, is much thicker. The zona granulosa is formed of several layers 

 of cells, instead of one only. Its membrana propria is much thicker, so 

 as to form a distinct fibrous, investment; the membrana Jibrosa and the 

 blood-vessels surrounding it are numerous, and may be said to form a 

 membrana vasculosa about it. 



