DISCUSSION 
the difference is not inherited. T. A. Davis finds that left- 
handed ones give 21 per cent more in nuts per year than right- 
handed ones. This would be a lunatic thing to search for; but 
if you find it you find it, and I think that a few lunatics let 
loose to look for ridiculous things like that might uncover some 
interesting facts in 4 or 5 years. 
I would finally add that I have seen water hyacinths being 
grown as pig food in Singapore. Chinese pig breeders use the 
water hyacinths along with urban food waste, and I 
don’t think they do it out of altruism for pigs, but because it pays 
them. 
Brock: As I see it, the final limiting factor in the feeding of 
the world’s population is going to be a small group of essential 
amino acids, which of course can be converted into protein 
equivalents. This will probably represent much less than the 
recommended allowance of, say, 70 grams of protein per day 
for the adult, or one gram per kilogram of body weight. When 
you get down to a pure amino acid diet, you can satisfy the 
requirements of man on something like the equivalent of 30 
grams of protein or probably even less than that. For a child 
you have to start with 3 grams per kilogram body weight for 
infants and then work down with advancing age to perhaps 
half a gram per kilogram for the adult—provided, of course, 
that this is what we call first-class protein containing an ade- 
quate balanced quantity of essential amino acids. It is clear 
that over a large part of the underprivileged world the protein 
available for the pre-school child is seriously deficient even for 
the present population. 
Crick: I wonder if we cannot find mutants which will 
contain a bit more lysine and tryptophan. How many proteins 
are there? How many mutation events would you need to 
obtain an adequate amount of lysine and tryptophan in maize? 
Pirie: Fowden has published figures on maize from Uganda, 
showing an extremely wide variation in the methionine and 
tryptophan content but lysine was always low. 
Hoagland: Maize has been cultivated so extensively and in 
so many different breeds from the wild form that it is very 
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