250 REPRODUCTION 



epithelial cells, known as Graafian follicles. A Graafian follicle 

 moves toward the surface of the ovary, ruptures, and dis- 

 charges the ovum, giving ri^e to the process of ovulation. 

 This is in most animals a periodic phenomenon, and in woman 

 probably begins at puberty with the first menstruation and 

 continues until the climacteric. Cases of pregnancy at the ages 

 of seven, eight, and nine years show that it may occur very early. 

 After the ovum has been set free from the ovary it in some 

 unknown manner reaches the Fallopian tubes. It is possible 

 that in woman, as has been observed in some animals, the 

 fimbriated ends of the tubes clasp the ovaries when the eggs 

 are discharged. The cilia lining the tubes gradually carry the 

 egg toward the uterus, which it reaches in from four to eight 

 days. 



Impregnation or fertilization usually takes place in the tubes 

 because the cilia, while they carry the ovum in one direction, 

 act as a guiding stimulus to the spermatozoa, which move in 

 the opposite direction to meet the ovum. In case the ovum is 

 fertilized it passes on to the uterus, where it is retained and 

 develops to the end of the embryonic period. 



The uterus is active monthly in that it discharges a bloody, 

 mucous liquid through the vagina. This is called menstruation. 

 Some days before the flow the mucous membrane of the body 

 of the uterus begins to thicken by the growth of its connective 

 tissue, and by the engorgement of its bloodvessels until it is 

 from two to three times its normal thickness. The swollen 

 capillaries become ruptured and the epithelial cells undergo a 

 degeneration. Usually only the superficial portions of the mucous 

 membrane are involved, and those cases where it is removed 

 to its deepest layers are very likely pathological. The flow 

 continues for four days or more, during which 100 to 200 c.c. of 

 blood are lost. The latter is slimy with mucus, does not coagu- 

 late, contains disintegrated tissue, epithelial cells, and has a 

 characteristic odor. Menstruation is accompanied by many 

 other symptoms. The ovaries and breasts are congested, dark 

 rings form about the eyes, mental depression often exists, skin 

 and breath have a characteristic odor. The intermenstrual 

 period exhibits a gradual increase in nervous tension and 

 metabolic activity, manifested in an increased production and 

 excretion of urea, in a higher temperature, and an increase 



