410 NUTRITION. 



not employed either for the restoration of lost materials, or for the 

 increase of mass in the body or its individual organs, or for the 

 accomplishments of any other objects of life, but is again given to 

 the external world, after having undergone certain alterations 

 which render it more capable of being excreted. There is, there- 

 fore, an actual superfluous consumption (Luxus-consumption, to use 

 C. Schmidt's expression), whenever there is this abundant supply of 

 food. In such a case the organism takes up far more than it 

 requires even for the most active accomplishment of all the vital 

 functions. The difficulty consists, therefore, simply in this, that 

 we are unable accurately to determine the mean which will give 

 the organism neither too little nor too much nourishment for the 

 maintenance in their normal equilibrium of all the movements of 

 matter, and the manifestations of force depending upon them. 

 Schmidt and Bidder have, therefore, designated as superfluous con- 

 sumption (Luocus-consumption) whatever exceeded the amount of 

 food which was shown in experiments upon fasting animals to be 

 absolutely necessary to life ; and hence they have taken the mini- 

 mum value of the metamorphosis of matter, as the unit with which ' 

 all further experiments on nutrition might be compared. 



In determining the absolute quantities of the nutrient sub- 

 stances, on which the metamorphosis of matter depends, there are 

 three magnitudes which we are especially called upon to consider : 

 the first is the quantity of food which will prevent the organism from 

 sinking by starvation ; the second is that which affords the right 

 supply of nourishment for the perfect accomplishment of the vital 

 functions ; and the last is that which indicates the sum of nutrient 

 matter which may under the most favourable circumstances be sub- 

 jected to metamorphosis in the blood. 



If \ve should succeed in ascertaining the mean amount of the 

 metamorphosis of matter, and consequently of determining the cor- 

 responding quantity of food, it would be very readily seen, that 

 like everything in the living organism, this amount will also vary 

 excessively according to existing conditions. It appears aln;ost 

 self-evident that there should be a greater consumption when all 

 the vital functions are in a state of unwonted energy, or during any 

 considerable or continuous manifestation of force, than in a state 

 of rest or vegetative passivity ; the previously noticed increase of 

 the urinary constituents, and the more profuse perspiration after 

 bodily exertion, have afforded the most positive proof of this fact. 

 The necessity for nourishment is, therefore, increased with the 

 increase of external activity (activity dependent on exertion) ; this 



