THE PHYSIOLOGY OF ALIMENTATION. 537 



to treat of the facts and applications, but a single functional act in 

 particular. It is then seen that the source of energy which this act 

 puts in play is found in the substance of the organ and in the active 

 tissue, and not in the aliment in the condition in which the animal 

 imports it from without. In other words, it is not the aliment in the 

 rough which is the source of energy, but the aliment digested, modi- 

 fied, elaborated, and incorporated as an integral part of the tissue 

 which employs it; in short, in the state of reserve. All the principles 

 of physiological energetics of which we have spoken apply to the ali- 

 ment as refined, and in this state only ; that is, as a part of the reserves. 

 Are they also applicable to the aliment in the strict sense of the word? 

 Only in another fashion. Between the substance of the aliment and 

 the substance of the reserves there are differences resulting froui the 

 various processes which have been employed from the time v^hen the 

 aliment was originally introduced into the organism to that .vhen it 

 becomes assimilated in its proper place. These preparations maybe 

 very numerous, and they are in most cases still unknown. It \ 3 gener- 

 ally admitted, however, that they are such as to use up so litth, energy 

 that its quantity may safely be neglected. The supposition is warranted 

 in certain cases, but, on the other hand, it is erroneous in a greater num- 

 ber. M. Chauveau has very clearly exposed this error of the theorists 

 on alimentation. He has been able to determine the amount of energy 

 so used in certain processes, by means of very ingenious experiments. 

 But this is not the place to discuss this matter. Nor shall we examine 

 the new and very interesting controversy on physiological dietetics. 

 We must restrict ourselves to incidentally indicating the most general 

 relations of the theory of alimentation with the subjects of our present 

 inquiry, which is to illustrate the fundamental principles of the ener- 

 getics of living beings. 



III. — THE PHYSIOLOGY OF ALIMENTATION. 



What is an aliment, and in what does alimentation consist? This is 

 a question which no one takes the trouble to answer — at least if he be a 

 physician, a physiologist, or a zoologist. A Frenchman who knows his 

 language will reply, like the dictionary, that "the term aliment is 

 applied to all those substances, of whatever nature, that habitually serve 

 or are able to serve the purposes of nutrition." The thing is easy to 

 understand; it is anything used by a decent man to nourish himself. 

 If you want to know more, ask the cook. 



That would be one solution; but there are many others. The prob- 

 lem of alimentation presents a thousand aspects. It is culinary and 

 gastronomic of course, but it is also economic and social, agricultural, 

 financial, hygienic, medical, and even moral. And first of all, and before 

 all, it is physiological. It is from this point of view that we shall dis- 

 cuss it here — solely and entirely that aspect which concerns the phe- 

 nomena of life. 



