THE HORMONE OF PREPARATION 



ovaries are the only effective source of estrogenj and if they 

 are removed all evidence of estrogenic action disappears. 



Recent investigations begin to hint that under special cir- 

 cumstances the adrenal glands may produce estrogenic hor- 

 mones. It is too early however to see what relation this has 

 to the general theory of the estrogenic hormones. 



Action of the Estrogenic Hormones 



Once the hormone gets into the blood stream, whether from 

 the subject's own ovaries, or by the experimenter's needle, it 

 is carried all over the body, through all the organs and tissues. 

 But — and this is characteristic of all the hormones — it is 

 selective in its action, like a key that opens certain locks and 

 not others. The major point of attack of this particular 

 hormone is the reproductive tract. This is strikingly seen if 

 we give small doses to an immature female animal, whose 

 uterus has never yet been subject to the action of estrogen. 

 Half an hour after an injection of the hormone the blood 

 vessels in the uterus begin to dilate and the blood to flow faster 

 through them, reddening the whole organ. The microscope 

 tells us that the rate of cell multiplication in uterus, Fallopian 

 tube and vagina is sharply increased. All the constituent tis- 

 sues of these organs become better defined or differentiated, 

 as the histologists say (see Plate XVI, A). The muscle cells 

 of the uterus grow longer and thicker and the uterine glands 

 increase in size. Plate XVI, B shows the remarkable stimula- 

 tion of growth and intensification of blood supply, produced 

 in a young rabbit, 10 weeks old, by treatment with estrogen 

 for 10 days. In two weeks or thereabouts, if the treatment is 

 continued, the baby rabbit develops a uterus of adult size; 

 but to the best of my knowledge, the hormone will not carry 

 the growth of the uterus beyond the normal mature state. 

 Further treatment, if forced, might cause damage to the 

 uterus but would not make a larger-than-normal organ. The 



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