World Population 
inhibiting dosages are so low compared to the dosages necessary 
to cause these effects on the embryo that the chances of pro- 
ducing an effect on the embryo are very remote. 
So far as other side effects of these compounds are concerned, 
these drugs act like hormonal steroids and the side effects are 
those which one would attribute to hormonal steroids; that is, 
one might expect to get effects on the pituitary which in turn 
are reflected on ovarian function and even on adrenal function. 
However, here again the dosages which inhibit ovulation are so 
low that no very marked effect on the other glands of internal 
secretion has been observed, at least so far. 
Lederberg: Dr. Parkes, you showed a rather startling curve 
of alteration of sex-ratio in the 1go1 series. There was a drop 
from 100 at birth to about go per cent ratio of males at mar- 
riageable age. Are there mortality statistics that would corro- 
borate that? 
Clark: ‘The South African war was on. 
Parkes: ‘The figures I think are all right, but mortality 
certainly does not account for the whole of it. Emigration 
was undoubtedly a big factor. 
Hoagland: You mentioned that during wartime—and 
especially during the first world war—the number of males 
went up relatively and then you mentioned later that younger 
marriages might be involved here. I am surprised that this 
would make any difference in the sex-ratio. 
Parkes: Younger marriages produce more males relatively, 
and the age of marriage decreased considerably during both 
war periods. 
Bronowski: Younger marriages and first children both pro- 
duce more males. 
MacKay: If males outnumbered females in the ratio 105: 
100, this would only mean that in every circle of 41 people, one 
(on the average) might be partnerless for this particular reason, 
namely that he was of the “‘excess”’ sex. In practice this factor 
would be embedded in so many others that affect people’s 
chances of marriage, that I wonder if we are not making too 
much of it. At the individual level it would be hardly detectable. 
i oe | 
