A HARD-WORKING DIET. 17 
It is one of the important discoveries of recent years padi 
that THESE COMBINATIONS, WHICH TAKE PLACE IN place in the 
THE WORLD AROUND US, ALSO TAKE PLACE IN OUR Sona ee 
OWN BODIES. ee 
We take in compounds of C, H, and N in our 
foods, we take in O from the air we breathe. 
The H combining with the O forms water, which 
leaves us as perspiration (more as invisible perspiration 
than in visible “sweat”), as moisture in our breath 
(visible on a frosty day), and through the bladder. 
The C combining with O forms carbonic acid, which 
leaves the body mostly through the lungs. 
The N combining with H forms ammonia, which 
leaves the body through the kidneys. 
The solid excreta which leave the body consist for 
the most part of actual waste—that is, material which 
has not been made use of at all. 
It is the knowledge of these forms of outgoings 
of oxidized C, and H—that is, C and H, which 
have within our bodies combined with the O we 
have taken in in our breath—and of ammonia that 
forms THE FOUNDATION OF OUR PRESENT WAYS OF The founda- 
r tion of our 
STUDYING FOOD VALUES. The quantity of C, H, present ways 
and N taken in as food is weighed, and the out- or ee 
goings in perspiration, breath, urine, and excreta are 
weighed. They have been ascertained for different 
conditions of exercise and different conditions of 
health, and to some extent for different conditions of 
surrounding weather, so that the intakings and the 
various outgoings of the body can be balanced up, 
like the introduction of raw material and the turning 
out manufactured stuff in a mill can be. 
That was a great advance when the genius and 
