206 STUDENTS HISTOLOGY 



FORMATION OF THE OVUM 



As has been previously shown, the ovary is covered with 

 columnar epithelium ; and, singular as it may appear, the 

 fifty thousand Graafian follicles, which it is estimated are devel- 

 oped during the life of the human female, have their origin in 

 these cells. 



During foetal life this surface epithelium undergoes a very 

 rapid proliferation, and chains of cells become imbedded in the 

 stroma of the ovary. These epithelial prolongations are called 

 ovarial or egg-tubes. A little later in the development, separate 

 portions or links of these chains are cut off by the ingrowth of 

 the stroma. The little groups of cells thus isolated become each 

 a Graafian follicle. 



Scattered among the columnar cells, larger, more nearly 

 spherical cells are also found, the primordial ova. These are also 

 imbedded in the substance, and one at least will always be found 

 among the minute collections of cells which have been isolated. 



In the process of development, each group of cells becomes a 

 Graafian follicle with its contained ovum, the columnar cells form- 

 ing the wall proper, and the primordial cell the ovum, with its 

 vesicle and germinal spot. 



PRACTICAL DEMONSTRATION 



The ovary from a still-born babe is to be removed with the scissors, 

 exercising the utmost care that the surface be not touched. The ovary of a 

 rabbit or guinea-pig may also be used with advantage. Place immediately 

 in strong alcohol, and in twenty-four hours it will be fit for cutting. Cut 

 extremely thin sections at a right angle to the free surface and including the 

 same; stain with haematoxylin and eosin; mount in balsam. 



OVARY OF HUMAN INFANT (Fig. 129) 



OBSERVE : 

 (L.) 



1. The free surface. (Note the occasional depressions which 

 mark the involution of the epithelial cells.) 



2. The layers. (Note the absence of demonstrable tunica 

 albuginea and the great area occupied by the cortex. The vessels 

 of the central portions are, unlike the ovary of mature life, large, 

 not numerous, and thin-walled.) 



