CONTENTS 



CHAPTER III. THE OVARY AS TIMEPIECE 



Development of the eggs of mammals to maturity at 

 regular intervals; occurrence, in most mammals, of a 

 phase of sexual responsiveness (estrus) at the time of 

 ripening of the eggs ; resultant mating, and fertilization 

 of the eggs ; the reproductive cycle constituted by recur- 

 rence of these events; peculiar modification of the cycle 

 in the human race, apes and higher monkeys, character- 

 ized by monthly disturbance in the uterus resulting in 

 menstruation. 



CHAPTER IV. THE HORMONE OF PREPARATION AND 



MATURITY 



Production by the ovaries of a remarkable substance, 

 the estrogenic hormone ; its property of causing the other 

 organs of the reproductive tract (oviducts, uterus, vagina, 

 mammary glands) to grow to adult size, and of main- 

 taining them in the adult state. 



CHAPTER V. A HORMONE FOR GESTATION 



Conversion of the ovarian follicle, after discharge of 

 the egg, into a temporary gland of internal secretion, the 

 corpus luteum; production by this gland of a hormone 

 called progesterone, which acts upon the uterus in such 

 a way as to insure attachment and nourishment of the 

 early embryo. 



CHAPTER VI. THE MENSTRUAL CYCLE 



Menstruation a peculiar phenomenon limited to a few 

 species of higher animals ; its period (in humans) about 

 four weeks, but not perfectly regular. Digression about 

 the cycle in general, showing that it is probably due to 



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