DISCUSSION 
spermatozoa has been known for many years, but the applica- 
tion of this principle to men and its fairly intensive study 
originates with the Japanese group that you mentioned. There 
is no question about the fact that you can reduce the number of 
spermatozoa markedly in this way. But the really important 
problem remains unsolved: what is the minimum number of 
spermatozoa necessary for fertility? As I mentioned, there are 
steroids which will reduce the sperm count markedly; in fact 
norethynodrel is one of them. In Puerto Rico we had some 
volunteers who agreed to take a substance, closely related to 
the ones I mentioned in my paper, which was mildly androgenic 
(that is to say, slightly masculinizing rather than feminizing). 
The sperm count could be reduced to zero with this, but in 
order to make sure there was no reduction in potency in these 
men, we gave a dose which reduced the sperm count to just a 
few million—anywhere from half a million up to perhaps 5 
million. And there was evidence that men with even the 
lowest count could still have offspring. In Puerto Rico this led 
to some small scandal, because one of the men claimed it was 
not he but some other man responsible for the pregnancy that 
occurred, and we dropped the study. Perhaps hot baths would 
be more acceptable to husbands—I don’t know. 
Parkes: ‘The difficulty about hot baths is that the raised 
temperature blocks spermatogenesis, but there will still be a 
reserve of functional sperm and until these have been got rid of 
fertility will persist. The integration of a cycle of hot baths and 
exhaustion of the epididymal sperm would be quite compli- 
cated. 
Pirie: The hot baths story is a bit older than you think. 
I have read, I think in Westermark’s History of Human Marriage}, 
that they were used with contraceptive intent in Roman times. 
Rather than damaging the testis by heat or other means so 
that it produces no sperm, I would think that vasectomy would 
be a simpler and more direct method. The objection to it has 
been that it is irreversible, resulting in permanent sterilization, 
but might it not be possible to reverse it if it is done with a more 
modern technique ? 
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