Metabolism Experiment No. 59. 



51 



body may be made by multiplying its amount in grams by its heat of com- 

 bustion. The results are stated in table 18. The total energy which would 

 result from the katabolism of the varying amounts of the protein, fat, and 

 glycogen is given in the last column. 



It should be here noted that these figures represent the total potential 

 energy of the different materials and not the actual energy liberated in the 

 body, for while in the katabolism of fat and carbohydrates the total heat of 

 oxidation is liberated, in the katabolism of protein a certain moiety is 

 eliminated as the potential energy of urine. 



Balance of Energy. 



As the total heat produced is derived from the katabolism of body protein, 

 fat, and carbohydrates, there should be an exact balance between the computed 



Table 19. Comparison of energy derived from katabolized body material loith 

 total heat production Metabolism experiment No. 59. 



total energy of the materials oxidized in the body and the total heat produced. 

 That such a balance exists, though it is not a perfect one, appears from a 

 consideration of table 19. Since, however, not all the potential energy of the 

 protein is actually liberated in its katabolism, the net energy from the body 

 protein is derived by deducting the potential energy of the urine from the 

 energy of the protein katabolized. This computation is made in the first three 

 columns of the table. The energy of body fat and glycogen katabolized are iden- 

 tical with the amounts shown in table 18. The total energy derived from the 

 different sources, therefore, is the sum of the net energy of the protein, the heat 

 of combustion of the body fat, and the heat of combustion of the body glycogen. 

 This total is recorded in column /. The total heat production shown in table 

 17 is recorded in column g above. Theoretically at least, we should expect that 

 the total heat production would correspond to the total energy derived from the 



