INFLUENCE OF FOOD. 359 



grammes of fat, 84*37 grammes of starch, 93*75 grammes of sugar, 

 120*80 grammes of malic acid, 65*23 grammes of albuminates, 

 73'77 grammes of collagen, or 68*01 grammes of (dry) muscular 

 substance. No one who has followed our development of physio- 

 logical chemistry can for a moment suppose that any one individual 

 substance taken from this series can of itself serve the purposes of 

 vitality, provided even it reach the organism in the equivalent 

 quantity ; and in the following section cur attention will be espe- 

 cially directed to the inquiry of the proportion in which several of 

 these substances require to be mixed in order to render them 

 capable of supporting the vital functions. These numbers must, 

 therefore, remain merely as proportional estimates of their relative 

 values in respect to the functions depending upon the interchange 

 of gases in the lungs. 



This table suggests another consideration, which may throw 

 some light upon the difference in the relations between the quan- 

 tity of oxygen which is absorbed and that which is exhaled in 

 the form of carbonic acid after vegetable and animal food respec- 

 tively, in as far at least as these relations have been made 

 known to us by the experiments of the inquirers already referred 

 to. If, for instance, we assume that the interchange of gases in 

 the lungs is for a time merely the result of the combustion of a 

 single one of the above-named substances, we should find, when- 

 ever pure fat was subjected to oxidation, that for every 100 parts 

 of absorbed oxygen 71*32 parts are contained in the carbonic acid 

 expired during the interchange of gases in the lungs, while in the case 

 of starch and all the other carbo-hydrates 100 parts are found in 

 the exhaled carbonic acid, in malic acid 110*53 parts, and in the 

 muscular substance 83*60 parts. When we compare these numbers 

 with the results obtained by Regnault and Reiset, Bidder and 

 Schmidt, and other investigators, we discover the reason why, 

 after vegetable food, a larger per-centage of the absorbed oxygen 

 is found in the expired carbonic acid than in the case of the 

 carnivora, for the food of the latter class of animals has relatively 

 more hydrogen to be consumed than the food of the herbivora, 

 and on this account we observe that the proportion exhibited in 

 fasting animals, which to a certain extent may be said to live upon 

 their own flesh, is very nearly the same as that noticed after the 

 use of an animal diet. 



The above remarks on the influence of the diet generally, show, 

 however, that the quantity, as well as the quality of the food, exerts 

 a very considerable influence on the amount of the interchange of 



