118 VARIOUS FOOD-PLANTS 
enough to yield about 1,900 Calories or 805,600 kilogrammeters of 
energy, which has been found to be approximately the amount ex- 
pended in 24 hours. If at first sight this seems to be an exaggerated 
estimate of the energy given out, it should be borne in mind that a 
very large share goes to keep up the warmth of the body; while of 
the remainder which is transformed into mechanical activity, a 
considerable proportion is used up in the muscular movements 
of the digestive organs, in breathing some 23,000 times, and in mak- 
ing more than 600,000 heart-beats, thus leaving only about one 
third of the whole available for locomotion and external work. 
The main point which here concerns us regarding the 
make-up of a proper daily ration is the relative proportion 
of nutrients rather than their absolute amount. On the basis 
of the figures given, it may be stated roughly and in a general 
way that 1 part proteid, 1 part fat, and 6 parts carbohydrate, 
would ordinarily meet the daily needs of an average person, 
or in other words that one’s food should be about § proteid, 
+ fat and 2 carbohydrate. In the rations recommended it 
is assumed that the foods chosen are easily digestible; for 
it is not what we eat but what we digest that nourishes us. 
For students and other brain-workers digestibility is of es- 
pecial importance since their largely sedentary life leaves 
them but little surplus energy to spare for unnecessary 
digestive work. 
A glance at the chemical chart (Fig. 120) will show that 
many vegetable foods do not have their nutritive constit- 
uents in anything like the standard proportion. This means 
that if a man were to obtain all his nourishment from such 
foods, he would have to eat too much of one ingredient 
(generally a carbohydrate) in order to get enough of another. 
When it is remembered that the dry substance of meats, fish, 
eggs, and other such foods of animal origin, consists almost 
entirely of proteids and fats, we see that here also there is a 
similar disproportion, although in another direction. Since, 
however, the constituents which are deficient on the one side, 
are in excess on the other, a mixed diet combining animal 
with vegetable foods, is most likely to be well-balanced. 
From this point of view it is interesting to notice how 
generally the instincts of mankind have led them to prefer 
combinations of food wherein the components supplement 
