THE GENERATIVE ORGANS. 2Og 



ing several layers, and the ovum becomes eccentri- 

 cally placed. There is still no cavity, but this soon 

 appears, at first as a slit between the cells, and then 

 grows wider and wider as fluid accumulates within 

 it. Changes in the interstitial tissue lead to the for- 

 mation of the theca folliculi, the epithelium directly 

 about the ovum assumes a radial arrangement, the 

 zona pellucida is formed, and we thus have the 

 structure of the maturing follicle, with which we 

 are acquainted. 



TECHNIQUE. 



Section of Adult Ovary^. The human ovary, or that of 

 a recently killed dog or cat, should be divided trans- 

 versely, great care being taken not to rub the surface, 

 since the germ-epithelium easily comes off, and placed in 

 a mixture of equal p^arts of one-quarter-per-cent. chromic 

 acid solution and alcohol. After a week it is to be 

 transferred to alcohol, in which in a few days it will 

 become sufficiently hard. A half is imbedded in cel- 

 loidin, the sections stained double and mounted in 

 balsam. 



Section of Developing Ovary. The ovary of a fcetal or 

 new-born animal is hardened and prepared as above. 



FALLOPIAN TUBES. 



The walls of the Fallopian tube consist of three 

 layers : an outer or serous layer, a middle or muscular 

 layer, and a lining mucous membrane. 



The serous layer consists of loose fibrillar connec- 

 tive tissue with elastic fibres, its free surface being 



