THE MANIFESTATIONS OF LIFE 83 



When we inquire into the meaning of the continuous 

 activity of normal life, as contrasted with the temporarily 

 suspended activity of fatigue and the permanently 

 suspended activity of death, we find it explainable 

 through a study of the nutritive or self-sustaining power 

 of the organism. 



Ordinary activity, exaggerated activity, exhausting 

 and fatal activity, being followed by varying degrees of 

 molecular disturbance through combustion, necessitate 

 varying degrees of molecular reintegration; i.e., the 

 introduction of new matter to replace what has been lost. 



Such new matter constitutes the food of the organism. 

 A food may therefore be defined as any substance 

 from which a living organism is able to derive material 

 for its sustenance or increase. 



It is a common observation that organisms beginning 

 their life histories as microscopic masses of protoplasm 

 eventuate in enormous numbers of simple or in enor- 

 mous masses of complex kind. This shows the natural 

 disposition of living substance to increase. Such in- 

 crease of numbers or size being possible only through 

 increase in the actual quantity of the living substance, 

 it becomes clear that that substance is endowed with the 

 capacity of forming more substance of its own kind. 



Living substance or protoplasm is the most complexly 

 compounded of all the substances known to the chemist. 

 Indeed it is so complex in chemical structure that its 

 exact composition is unknown and no correct formula 

 for it has been worked out. 



Protoplasm stands at the head of a list of compounds 

 known as proteins, some of which are well-known, yet 

 not one of which is correctly known as regards its true 

 chemical composition. The reason becomes obvious 

 when a few of the formulae suggested are examined. 

 Thus one chemist who studied the hemoglobin from 

 the dogs' blood finds it represented by the formula 

 C 726 H 1171 N 194 214 S 3 . One of the various formulae sug- 

 gested for egg-albumen is C 204 H 322 N 52 O 66 S 2 . The com- 



