4 APPLIED PHYSIOLOGY 



individual vegetarians, and of vegetarian races, for 

 example, revealed the fact that health and activity 

 could apparently be maintained on much smaller allow- 

 ances of protein than the Voit standard postulated. 

 Finally there came the well - known experiments of 

 Chittenden, which showed for the first time on a suffi- 

 ciently large scale that, beyond all apparent doubt, 

 health and efficiency could be maintained for indefinite 

 periods upon a much smaller protein intake than 

 118 grammes. Chittenden fixes the protein optimum, 

 indeed, or the best amount for habitual consumption, at 

 about 60 grammes per day, which is not far above the 

 minimum upon which nitrogenous equilibrium can be 

 maintained. Any intake above this he would regard as 

 a luxus consumption.* 



* It might seem that in human milk we would find a standard 

 v/hich would furnish a guide to the proper proportion of protein 

 which the diet ought to contain. 



An infant of six months, weighing 6*7 kilogrammes, and con- 

 suming an average quantity of breast milk (950 grammes), consumes 

 about 14 grammes of protein, and has a total energy intake of 

 594 Calories per day. This is about 2 grammes of protein per 

 kilogramme, and if an adult of average weight (70 kilogrammes) 

 consumed the same proportion of protein, he would require 

 140 grammes in his diet, which is much above even the Voit 

 standard. 



There is, however, another way of looking at the question : Of 

 the total Calories taken in by the infant, fifty- seven are derived 

 from protein ; and assuming the adult to require an intake of 3,000 

 Calories per day, and that the same proportion of these is derived 

 from protein as in the child, then the amount of protein the adult 

 should consume would only be about 70 grammes per diem, which 

 is approximately Chittenden's standard. Which is the correct way 

 of looking at the question it is difficult to say. If the adult is to 

 take as much protein per unit of his body-weight as the child, then 



