WHAT TO EAT 143 



121. Nutritive ratio. It would be possible for a person to 

 subsist on a protein diet, since these nutrients are also oxidized 

 in the cells, and yield energy; and many animals and some 

 plants do actually get along on proteins alone. But a sur- 

 plus of protein puts an additional burden upon our livers and 



Fig. 79. The respiration calorimeter 



In the large chamber a man can live for several days or weeks under conditions that 

 give an accurate account of his body's income and expenditure, in the way of matter 

 as well as in the way of energy. A, door and window; B, door for food etc.; C, tank 

 for catching water circulating through the walls of the chamber; D, observer's table, 

 with devices for measuring and regulating temperature etc.; E, rubber bag to equal- 

 ize the air pressure within the chamber; F, apparatus for circulation and purification 

 of air in the chamber. (From photograph furnished by Office of Home Economics, 



United States Department of Agriculture) 



kidneys, besides being relatively more expensive financially. It 

 is really worth while to reduce the protein in food to the lowest 

 proportion of practical safety. This proportion of protein in 

 the diet is called the nutritive ratio. In countries which have 

 relatively cheap supplies of meat there has been a tendency to 

 consume an excess of proteins. The best studies we have point 



