io 7 6 REPRODUCTION 



supposed that they are of importance. When the prostate and the 

 seminal vesicles are removed in white rats, the female is no longer 

 fertilized, although the sexual power of the male is unaltered. The 

 testes apparently develop spermatozoa in the normal manner, but 

 for some reason they either do not reach the ovum or do not react 

 with it normally if they do reach it. When the testes are re- 

 moved from a young animal, the development of the prostate is 

 interfered with; in an adult animal the gland atrophies. 



The ovum also begins as a typical cell with nucleus (germinal 

 vesicle), nucleolus (germinal spot), centrosome and attraction sphere 

 (p. 5), and it forms, by its repeated subdivision, all the cells of the 

 foetal body. But, except in some (partheno genetic) forms, it never 

 awakens to this reproductive activity till fecundation has occurred ; 

 and fecundation essentially consists in the union of the male with the 

 female element, or rather in the union of the male and female nucleus. 



From time to time a ripe Graafian follicle, overdist ended by its 

 liquor folliculi, bursts on the surface of the ovary and discharges an 

 ovum. The common opinion is that most ova are discharged at the 

 time of the menstrual period, but some writers take the view that 

 the discharge bears no relation to menstruation. Only one ovum 

 seems to be shed each month. It was formerly believed that the 

 frayed or fimbriated end of the Fallopian tube, rising up finger-like 

 from the dilatation of its bloodvessels, grasps the ovum. But it is 

 more than doubtful whether this occurs. It is more probable 

 that the ovum is first discharged into the pelvic cavity, and 

 is guided to the orifice of the Fallopian tube, not necessarily 

 that of its own side, by the movements of the cilia around the 

 orifice, and then passed slowly along the tube by the downward 

 lashing cilia which line it. Probably the ovum takes as a rule eight 

 or ten days to reach the uterus, and it is during this time that 

 fertilization takes place. If not impregnated, it soon perishes amid 

 the secretions of the uterus how soon has been matter of discussion, 

 and can hardly be considered as settled. If, however, impregnation 

 occurs, the ovum penetrating the superficial epithelium into the 

 subepithelial connective tissue becomes fixed in one of the crypts or 

 pouches of the uterine mucous membrane (decidua serotina), which 

 grows round it as the decidua reftexa. The Graafian follicle, after 

 the discharge of the ovum, fills up with blood, and a cellular struc- 

 ture, the corpus luteum, is developed in its interior from the cells 

 which line the follicle. In the absence of impregnation the corpus 

 luteum begins to disappear before the next menstrual period, and is 

 spoken of as a false corpus luteum. But when pregnancy occurs, it 

 continues to grow till the fourth or fifth month of pregnancy, and is 

 called a true corpus luteum. 



Menstruation. In the mature female, from puberty, the age at 

 which the reproductive power begins (thirteenth to fifteenth year), 



