November 3, 1916] 



SCIENCE 



627 



that the amount of urea excreted rises and 

 falls, except for a certain starvation mini- 

 mum, in direct proportion to the amount of 

 albuminous food eaten. The excess over 

 the starvation minimum was looked upon 

 as "luxus consumption" — an ungoverned 

 oxidation, due to simple chemical factors. 



But the matter was soon carried further 

 by the physiologists — particularly by 

 Pfluger, and by Voit and his pupil Rubner. 

 It was found that, other conditions being 

 equal, the consiunption of oxygen is within 

 wide limits independent of the abundance 

 of its supply, and that the actual consump- 

 tion of oxygen per unit of body weight is 

 very little different during starvation from 

 what it is when abundant food is supplied. 

 In starvation more fat is being oxidized to 

 compensate for the deficiency in albuminous 

 oxidation. Finally, the brilliant work of 

 Rubner established the fundamental fact 

 that within very wide limits different food 

 substances are simply substituted for one 

 another within the organism in direct and 

 exact proportion to the energy which they 

 furnish when broken down. The energy 

 liberation per unit body weight is prac- 

 tically constant, but if excess of food is 

 taken the excess of potential energy is 

 stored up as fat and glycogen, while if food 

 is withheld the stored excess is used up. 

 Even when all the stored fat and glycogen 

 is used up, the organism finally flings its 

 own living structural substance into the 

 balance, and in this last desperate effort to 

 maintain the normal metabolism the nitro- 

 genous oxidation again rises to an amount 

 which for a short time compensates for the 

 energy previously yielded by fat. "When 

 death from starvation at length comes the 

 old flag — the flag of life — is still flying. 



The massive work of Atwater and his 

 pupils on human nutrition, in which it 

 was shown that the normal daily food re- 

 quirement of a man is about 3,500 calories 

 in energy-value, was of course a direct ex- 



tension of the idea of normal nutrition. 

 "We maintain an energy consumption of 

 about 3,500 calories, just as we maintain 

 about 5.6 per cent, of C0 2 in our alveolar 

 air, or hemoglobin of 18.5 per cent, oxygen 

 capacity in our blood, or legs of a certain 

 length and anatomical structure. By a 

 strange confusion of ideas the idea is 

 abroad that nutrition is a matter of simple 

 chemistry and physics, and that when we 

 estimate food values in calories, we are ex- 

 emplifying this fact. This is enough to 

 make a staunch old vitalist like Harvey or 

 Johannes Miiller turn round in his grave 

 and laugh. What is it in the body that 

 measures out or withdraws protein, carbo- 

 hydrate and fat with meticulous accuracy 

 in terms of their energy value, in such 

 amount as to maintain the normal energy 

 metabolism? Is it not the vital spirit or 

 vital force? the old physiologists would 

 ask. Is not this phenomena of a piece with 

 all the other distinctive phenomena of life, 

 and ought not physiology to face these phe- 

 nomena fairly and squarely and generalize 

 from them, not run away from them ? This 

 is the question I am trying to put to you 

 now. 



Now I wish to make it clear that it is not 

 vitalism, but simply biology, that I am 

 preaching. Vitalism is a very roundabout 

 and imperfect attempt to represent the 

 facts. Physiological study, and biological 

 study generally, seems to me to make it 

 clear that throughout all the detail of 

 physiological "reaction" and anatomical 

 "structure" we can discern the mainte- 

 nance of an articulated or organized nor- 

 mal. This idea brings unity and light into 

 every corner of physiology. In other words, 

 it helps us within limits to predict, just as 

 the ideas of unalterable mass and energy 

 help us within limits to predict, or the ideas 

 of time and space help us within limits to 

 predict. I claim nothing more for it, but 

 also nothing less. The idea of life is just 



