DISCUSSION 
another group which Brock did well to mention that includes 
aluminium. Experimentally, when you give aluminium salts 
to mice you completely arrest the ovarian cycle. Some years 
ago there was anxiety about whether enough aluminium salts 
might remain in some baking powders to produce effects on 
peptic ulcers or even perhaps on ovogenesis and spermato- 
genesis. 
Clark: Do you object to aluminium kitchen implements? 
Klein: In man nothing definite has been shown, but in 
experimental animals such additives are dangerous. 
Glikson: I should like to make a general remark with refer- 
ence to Colin Clark’s paper. His plan for a world population 
of 45,000 million people seems to be based on a calculation of 
a person’s physical minimum requirements, and the earth’s 
resources of cultivable land. I cannot discuss the accuracy of 
this calculation, but I think a distinction must be drawn between 
a level of bare survival and the level of living a full life. Even if 
the calculation were correct, the 45,000 million would be just 
able to survive. 
Clark: No. They could live at the physiological maximum— 
ten times as many could survive at the minimum level. 
Glikson: ‘‘Survival”’ is not a human condition which pro- 
mises a balanced existence or peace for any length of time; this 
notion disregards the need of land, space and commodities for 
the creation of any values other than basic calories and a few 
vitamins. Space must be available for the great variety of 
human requirements of land use and ways of living. Some land 
“surplus”? appears essential for the establishment of a satisfac- 
tory community life. 
In considering possible future population densities, I would 
have expected to hear of research, not about minimum food 
requirements, but about the optimum diets to be provided as 
a basis for happier and healthier human lives. Obviously 
such research would have to be done on a regional basis taking 
account of all the varying environmental conditions and the 
physical and psychological human requirements of each region. 
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