REPRODUCTION 3 1 1 



are already present and grow downward with the epithelium 

 of the tube. The first appearance of the follicle, that is, the 

 formation of the primordial egg, occurs in the embryo. At 

 first the follicles are only 0.03 mm in diameter. When fully 

 developed they pass through the deep layers of the stroma 

 to the surface of the ovary. 



3. Ovulation or discharge of the ovum. The discharge 

 of the egg takes place by the bursting of the ripe Graafian 

 follicle. This bursting is accomplished by the increase of 

 liquid in the follicle whereby it is enlarged and its walls are 

 rendered tense until they burst. 



In the place formerly occupied by the follicle a cicatrix is formed 

 which is colored yellow by pigments : corpus luteum. 



The contents of the follicle, including the egg, lying 

 among the cells of the discus proligerus, reaches the end of 

 the oviduct, whose fimbriated end lies close to the surface of 

 the ovary. By the ciliated epithelium the egg is carried 

 through the oviduct to the uterus. 



In human females the discharge of the egg occurs regularly 

 every four weeks. It is accompanied by a capillary bleeding 

 from the mucous membrane of the uterus menstruation, last- 

 ing from two to three days. The hemorrhage is preceded 

 by a separation of the mucous membrane and the formation 

 of a membrane, the decidua menstrualis, which is afterward 

 cast out. During menstruation 100-200 g blood are lost. 



4. The maturation of the egg. Previous to fertilization 

 certain changes take place in the egg which are collectively 

 called the maturation of the egg. The nucleus of the egg 

 moves towards the periphery and divides by indirect division 

 into two nuclei. One of these, called the polar body, is cast 

 out of the egg. The other nucleus again divides into two, 

 one of which, the second polar body, is also cast out. The 

 remaining nucleus, called the female pronucleus, travels to 

 the centre of the egg. 



