424 NUTRITION. 



edge with regard to the metamorphoses which these prin- 

 ciples undergo ; and it is equally impossible to fix the rela- 

 tive calorific value of the deposition of new material in repair 

 of the tissues, and the change of their substance into eifete 

 matter in disassimilation. 



From these facts, and other considerations that have 

 already been fully discussed under different heads, it is evi- 

 dent that the physiological metamorphoses of nitrogenized 

 matter bear a certain share in the production of animal 

 heat ; although, in connection with inorganic matter, their 

 chief function seems to be the repair of the tissues endowed 

 with the so-called vital properties. 



What is the relation of the consumption of non-nitro- 

 genized matter to the production of animal heat ? 



It has been impossible to treat of the relations of the 

 non-nitrogenized elements to nutrition without considering 

 more or less fully the part these principles bear in the pro- 

 duction of heat ; and we must refer the reader to the pre- 

 vious chapter for a discussion of certain of these points. 1 

 In this connection, we will simply state the relations that 

 this class of principles is known to bear to calorification, and 

 the facts upon which our statements are based. 



It has been pretty clearly shown that both sugar and fat 

 are actually produced in the organism, even when the diet 

 is strictly nitrogenized in its character; but we will only 

 consider the relations of the non-nitrogenized elements in- 

 troduced into the body, assuming that the principles of this 

 class appearing de novo in the organism are the result of 

 transformation of nitrogenized substances. 



As far as the destination of the amylaceous, saccharine, 

 and fatty elements of food are concerned, we only know that 

 they are incapable, of themselves, of repairing muscular tis- 

 sue, and that they cannot sustain life. They are never dis- 

 charged from the body in health in the form under which 

 they enter ; but are in part or completely destroyed in nutri- 



1 See page 378, et seq. 



