OF FOOD. 105 



CHAPTER V. 



OF FOOD. 



the term " food" are included all those substances, solid 

 and liquid, which are necessary to sustain the process of nutrition. 

 The first act of this process is the absorption from without of all 

 those materials which enter into the composition of the living frame, 

 or of others which may be converted into them in the interior of 

 the body. 



The proximate principles of the first class, or the "inorganic 

 substances," require to be supplied in sufficient quantity to keep up 

 the natural proportion in which they exist in the various solids and 

 fluids. As we have found it to be characteristic of these substances, 

 except in a few instances, that they suffer no alteration in the in- 

 terior of the body, but, on the contrary, are absorbed, deposited in 

 its tissue, and pass out of it afterward unchanged, nearly every one 

 of them requires to be present under its own proper form, and in 

 sufficient quantity in the food. The alkaline carbonates, which 

 are formed, as we have seen, by a decomposition of the malates, 

 citrates and tartrates, constitute almost the only exception to this 

 rule. 



Since water enters so largely into the composition of nearly every 

 part of the body, it is equally important as an ingredient of the 

 food. In the case of the human subject, it is probably the most 

 important substance to be supplied with constancy and regularity, 

 and the system suffers more rapidly when entirely deprived of 

 fluids, than when the supply of solid food only is withdrawn. A 

 man may pass eight or ten hours, for example, without solid food, 

 and suffer little or no inconvenience ; but if deprived of water for 

 the same length of time, he becomes rapidly exhausted, and feels 

 the deficiency in a very marked degree. Magendie found, in his 

 experiments on dogs subjected to inanition, 1 that if the animals 



1 Comptes Rendus, vol. xiii. p. 256, 



