World Population 
salt, but found that the unevenness of consumption of salt ruled 
that out completely. 
Wright: My suggestion was something like a condiment 
which individuals could take at will, which would not normally 
be universally consumed: not, for example, putting it into 
cereal products, which would be consumed by a whole popula- 
tion. 
Parkes: Surely that could be done with existing com- 
pounds; you could presumably put norethynodrel into salt as 
well as into a pill. The whole point of putting things in the 
food is to reduce the whole population to a lower level of 
fertility. But on the occasion Dr. Pincus referred to in 1959, in 
India, it was stated that although that might be the only 
effective way, it would be entirely unacceptable, however much 
the country might be in demographic difficulties. 
Hoagland: A group of Japanese scientists has demonstrated 
(and this has been confirmed by an American group) that hot 
baths (45°c) of 15 minutes’ duration, taken three days running, 
will reduce a man’s sperm count very substantially below the 
number likely to be effective in fertilization; and if this were 
repeated every 2 weeks a fair degree of sterility could be 
attained. I would like to know if this is correct and if the 
application of this would be practicable. I had a debate with 
some Roman Catholic friends recently and asked whether 
taking hot baths would be regarded as contrary to natural law. 
The answer was that it would be, if taken for the purpose of 
contraception, but if you just took hot baths to be clean that 
was another matter. I also asked, supposing it were possible to 
regulate the rhythm method by chemical means so that it was 
reliable and that ovulation would occur precisely within a 
period of, let us say, 36 hours, would this artificial control be 
acceptable, or would this be contrary to “‘natural law’? It 
was said this would probably be acceptable. Would you com- 
ment on the practicality of regulation of the rhythm by steroidal 
substances as well as the practicality of the hot baths, Dr. 
Pincus? 
Pincus: The effect of heat in reducing the production of 
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