92 HUMAN PHYSIOLOGY. 



COMPARISON OF THE INGESTA AND EGESTA. 



Ingesta. Egesta. 



Proteids . . . 120 grams. Urea .... 40 grams. 



Fat .... 90 Inorganic salts. 32 



Starch . . . 330 ." Feces .... 104 " 



Inorganic salts. 32 " Carbon dioxid . 800 " 



Water . . . 2,800 " Water . . . 3,096 " 

 Oxygen . . . 700 " Total . ."4^72 " 



Total . . 4,072 " 



Other estimates as to the amount of the organic substances required 

 daily are as follows : 



The Energy of the Animal Body. The food consumed daily not 

 only repairs the loss of material from the body, but also furnishes 

 the energy to replace that which is expended daily in the shape of 

 heat and motion. All the energy of the body can be traced to the 

 chemic changes going on in the tissues, and more particularly to those 

 changes involved in the oxidation of the foods. 



The amount of heat yielded by any given food principle can be 

 determined by burning it to carbon dioxid and water, and ascertain- 

 ing the extent to which it will, when so liberated, raise the tempera- 

 ture of a given volume of water. This amount of heat may be 

 expressed in calories. A calorie is the amount of heat required to 

 raise the temperature of one kilogram of water one degree Centi- 

 grade. 



The following estimates give, approximately, the number of calories 

 produced when the food is reduced within the body to urea, carbon 

 dioxid, and water : 



i gram of proteid yields 4,124 kilogram calories, 

 i " fat " 9,353 



i " starch 4,n6 



The total number of kilogram calories yielded by any given diet 

 scale can be readily determined by multiplying the preceding factors 



