396 PHYSIOLOGICAL CHEMISTRY. 



below. First, however, a general method of calculating the 

 energy liberated as heat will be given. 



CALCULATION OF KINETIC ENERGY OF FOOD. 



In illustration of this we may make use of the example given 

 in the last chapter and employ a method which in principle is 

 very simple. The income of energy is due to the consumption 

 of certain weights of protein, fat and carbohydrates, the last 

 of which we may assume is made up of 9 parts of starch and 

 i part of cane sugar, all weights referring to the anhydrous 

 condition. The effect of the oxidation of sulphur and phos- 

 phorus will be neglected here, and the protein will be assumed 

 pure carbon, hydrogen, oxygen and nitrogen. We have then 

 as income: 



From 150 gm. protein, 150 X 57oo = 855,000 



1 10 gm. fat, no X 9400 = 1,034,000 



440 gm. carbohydrate, 440 X 4180 = 1,839,200 



3,728,200 



In small calories the whole income is therefore equivalent to 

 3,728,200 cal. 



We have next to calculate the potential energy of the food 

 stuffs not actually consumed, which are left in the feces and 

 the urine, and also the energy of any substance which may be 

 put down as a gain in weight in the body. Recalling the data 

 of the experiment in the last chapter we have 



T 33 gni. feces with 16.2 gm. C. 

 1,424 gm. urine with 20.4 gm. N. 



Calculating the N of the urine as urea, which in practice would 

 not be quite accurate, we have 44 gm. of that substance. The 

 organic matter of the feces corresponds approximately to 22.5 

 gm. of bodies resembling protein and 5.5 gm. of bodies resem- 

 bling fats, and these data we can now employ in the calcu- 

 lation. 



The illustration gave also a gain of 80 gm. of fat. The 

 solid matter lost in the form of perspiration is so small that 



