HOW FOODS MEET BODY NEEDS. 37 
Another use for the charts is in showing what foods can be com- 
bined to make a complete ration. For a complete ration the sum of 
the energy from all the foods included should equal 100 per cent, and 
similarly with protein, calcium, phosphorus, and iron. Although 
there is no disadvantage and probably considerable advantage if 
the totals for calcium, phosphorus, and iron are higher than those 
for energy and protein. The completeness of a ration can be tested 
by adding together the percentages of the constituents shown on the 
charts. In classroom or lecture use it may be more effective to fill 
in the lines on a skeleton chart as the different foods making up a 
ration are discussed. Allowance must also be made for bulk and 
vitamines. As pointed out on page 4, these are necessary elements 
of the diet although they can not be definitely measured. 
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