NORMAL AND PATHOLOGICAL GROWTH 161 



dermal tissues, the muscular and supporting tissues, and in the 

 vascular supply of the vaginal and uterine walls, and in the 

 mammary glands. 



The changes in rats and monkeys are accompanied by all the 

 phenomena of oestrus, and are accomplished within a time in- 

 terval equivalent to that of the oestrus of the normal animal. 

 The growths can be induced in female rats at an age many days 

 earlier than that of the normal puberty, or in rats or monkeys 

 that have had the ovaries removed, in which normal oestrus no 

 longer occurs. 



When injections of the artificially prepared hormone are 

 stopped, overgrowth ceases and a degree of degeneration oc- 

 curs. This type of overgrowth and its following retrogression 

 are characteristic of the preliminary stages in the reproductive 

 cycle in all mammals. It is, in fact, the structural basis of the 

 oestrous cycle. This is indeed a highly specialized type of 

 growth-producing influence, nevertheless, it is of most vital im- 

 portance in the physiological economics of the propagation of 

 the mammalian species. The unique and classic contribution of 

 Allen and Doisy consists in reducing the oestrous phenomenon 

 to a definite causative basis, in demonstrating that a single 

 hormone, abundant in the ovarian follicle, is the essential causa- 

 tive factor in the cylic oestrus and menstrual changes in the 

 maturing female. 



The later publications of Allen and his colleagues establish 

 the presence of this reproductive hormone in many other tis- 

 sues, — the corpus luteum in the human, the growth which fills 

 the cavity of the follicle when the ovum is discharged, the pla- 

 cental and fetal membranes of the human, the bovine, and 

 other mammals. It is evident that the follicular hormone plays 

 a very essential part in the growths and maturity of the body 

 during adolescence, and in particular during the succeeding 

 active reproductive years. It is also evident that the atrophic 

 changes in the organs of the reproductive apparatus and the 

 deviations from type in the growth and development of the 



