Control of Reproduction in Mammals 
allegedly had no such symptoms previously but had them 
“induced”? by the medication. Therefore these occurrences 
appear to be random events and exhibit no consistent relation- 
ship to medication. 
After the initial four to six months of use of this drug by a 
first group of volunteers, we questioned them about weight 
changes, breast size, menstrual flow, pain during menstruation, 
libido and frequency of coitus. Except for some tendency, not 
unexpected, to a decrease of menstrual flow, no significant 
changes were noted, the decreases tending to balance increases. 
It is clear from the foregoing that effective inhibition of 
ovulation by oral medication has been definitely accomplished 
in the human being. Rice-Wray and Goldzicher have recently 
reported on comparative studies with 2,432 women observed 
in 22,948 treatment cycles. Five progestin-oestrogen prepara- 
tions were used with complete effectiveness upon proper use of 
the regimen in which tablets were taken daily from the 5th to 
the 25th day of the menstrual cycle. Regularly achieved ovula- 
tion control may therefore be taken as a fact. Indeed, contra- 
ceptive research projects with steroidal ovulation inhibitors have 
been conducted throughout the United States, in certain 
European countries, in Japan, Ceylon, Singapore, Hong Kong 
and India, with remarkably similar data coming from each. 
CONTROL OF THE DEVELOPMENT OF THE FERTILIZED OVUM 
Our studies on the control of the development of the fertilized 
mammalian egg originated over 20 years ago when Dr. N. T. 
Werthessen and I followed up an original observation by Dr. 
George W. Corner. Corner found that in rabbits whose ovaries 
were removed shortly after fertilization the egg enters the uterus 
at the normal time but fails to grow to normal size or to implant. 
However, with the administration of an adequate dose of pro- 
gestin to such animals both normal ovum growth and implan- 
tation may be restored. Dr. Werthessen and I developed this 
Ovum response as part of a quantitative assay for progesterone. 
We found, furthermore, that oestrogens administered with the 
progesterone could inhibit the growth of the ovum and/or the 
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