No. 4.] 



CLEAN MILK. 



57 



To make direct comjiarison between foods, however, is diffi- 

 cult, for several factors must be taken into account. To com- 

 pare foods directly upon the basis of the amount of dry matter 

 contained in them is improper, for the reason that the char- 

 acter of such material varies greatly in value ; to make direct 

 comparisons upon the basis of the amount of protein (muscle- 

 making foods) that they carry is equivalent to stating that 

 the heat and energy carrying portions are of no value, which 

 is, of course, not true, they l)eing required in seven to ten 

 times as great quantities as the former; to make comparisons 

 directly upon the number of units of energy liberated is like- 

 wise improper, being equivalent to saying that the protein is 

 of no value, which again is untrue. So then, in order to com- 

 pare one food against another, it is necessary to compare those 

 foods which have similar proportions of digestible protein 

 and energy-bearing nutrients ; or, in other words, to compare 

 foods which have similar nutritive ratios, and are either both 

 of auiuial or both of vegetable origin, for the digestibility of 

 milk and meat products is very materially greater than that 

 of cereals and garden vegetables. In the following tables the 

 foods are grouped so that those of approximately like nutri- 

 tive ratios are compared against each other. 



Table 3. — Comparison of Foo<ls, showing Waste Matter and Digest- 

 ible Nutrient} 



» Adapted from Farmer's RuUetin 142, United States Department of Agriculture. 

 ' Aver.ageof 12 fair samples collected in HiirliiiKton, Vt. 



