THE HORMONES IN HUMAN REPRODUCTION 



a few red blood cells from time to time, beginning on the 3d 

 day, but no external bleeding. The experiment shows that 125 

 international units of estrone will substitute in many cases, 

 but not in all, for the natural product of the animal's own 

 ovaries, as tested by the prevention of postcastration bleed- 

 ing. A somewhat larger dose would obviously be required to 

 prevent such bleeding in every case. 



A variation of this experiment is to give castrated female 

 monkeys large doses of estrogenic hormone and then drop the 

 dosage until bleeding sets in. A number of such experiments 

 were reported by S. Zuckerman of Oxford, England, in 1936. 

 This investigator found that whenever he reduced the daily 

 dose from several hundred or several thousand international 

 units to any amount below 200 international units, estrin- 

 deprivation bleeding occurred thereafter. With more than 200 

 international units daily no bleeding occurred. 



These observations suggest that the output of estrogenic 

 hormone from the normal ovaries, which is of course sufficient 

 to prevent estrin-deprivation bleeding, may be about 150 or 

 200 international units. 



A third means of estimating the probable amount of estro- 

 genic hormone produced by the monkey is provided by the 

 fact that the so-called sex skin (the red swollen areas of the 

 rump and thighs) is under the control of the hormone. Re- 

 moval of the ovaries leads to shrinkage and pallor of the sex 

 skin, whereas administration of an estrogen in sufficient 

 amount will within a few days restore the color of this region. 

 One of my animals, a young adult, had its ovaries removed at 

 a time when its sex skin was in exceedingly florid condition. 

 The whole area over the rump, the back of the thighs, and the 

 ventral side of the base of the tail was swollen, thrown into 

 distinct ridges and deep red in color. After the operation, but 

 on the same day, the color and swelling were slightly reduced, 

 owing no doubt to the stress of the operation. One hundred 

 twenty-five international units of estrone was given daily 



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