374 ON THE PLACE OF FISH IN 



Briefly, carbon enters through the mouth as some 

 form of compound, becomes oxidized in the body, 

 giving rise to heat and force, and leaves the body 

 as carbonic acid. 



Hydrogen enters also as some compound, becomes 

 oxidized in the body, giving rise to heat and force, and 

 leaves the body as water, mostly in the breath. 



The amounts given off have to be supplied by foods 

 (see p. 353). 



Nitrogen. 



1. The union of N with H forms ammonia. 



2. The N taken into the body in foods leaves it as 

 ammonia. 



3. A calculation of the amount of ammonia given 

 off tells therefore the amount of N given off. 



4. The amount given off has to be supplied by 

 foods (p. 353). 



5. Muscle cannot be formed without N. 



6. It appears from experience that a HARD- 

 WORKING DIET must be largely made up of nitro- 

 genous compounds compounds which contain all the 

 four elements, C, H, O, N (p. 358). 



These must be accompanied by carbon compounds. 



7. There are some fish, herring, mackerel, sprats, &c. 

 (see pp. 362 to 364), which have nearly the same N value 

 as beef, mutton, or pork, and, so far as chemistry can 

 tell, hard work can be done on them as well as on meat. 



8. We are without the direct evidence of experience. 



The average daily requirements of those doing only 

 moderate work is (see p. 354) C, 4,900 grains; N, 

 300 grains. 



