400 



THE QUARTERLY REVIEW OF BIOLOGY 



in the case of both fed and starved flies. 

 Then age may be expressed in both cases as 

 hundredths, or centiles, of their own life 

 span in the case of each group of flies. 

 When this is done, with the result shown in 

 figure 6, it is seen at once that while com- 

 plete starvation reduces the absolute aver- 

 age length of life from about 45 days to 

 about 45 hours, the form, or shape, of the 

 survivorship curve remains unaltered. 



In carrying out these experiments dif- 

 ferent densities of population were used. 

 This circumstance led to the second sig- 

 nificant result, which is shown graphically 

 in figure 7. 



The net result of these experiments is 

 evident from the diagram. Under condi- 

 tions of complete starvation different 



adaptation of Cuvier's old "whirlpool" 

 conception of the organism. 



The concept of the organism embodied 

 in this scheme is, of course, an old one. 

 Lately Pikler has discussed a similar but 

 more detailed and complete outline of the 

 relation of organism and environment. 



What the organism does under experi- 

 mental conditions such that we can ob- 

 serve B of the above scheme free from the 

 disturbing influence of A, I have chosen to 

 call expressions of inherent vitality. In- 

 herent vitality may be precisely defined as 

 the total -potential capacity of an organism to 

 perform vital actions, in the complete absence 

 of exogenous derivation of matter or energy. 

 From the standpoint of energetics solely 

 it is analogous to the potential energy of 



->B- 



->C 



External Sources of Energy and 

 Non-Living Matter 

 (Food. Either chemical com- 

 pounds of external origin which 

 yield energy and utilizable ma- 

 terial when split by the organism 

 (animals), or similar compounds 

 synthesized by the organism itself, 

 with energy derived from light, 

 and subsequently split to yield 

 energy and utilizable material.) 



The Organism 



(An aggregation of matter 

 which has the property of auton- 

 omously changing A to C, by 

 virtue of its pattern or organization.^) 



The Product 



(Either (a) heat, (£) work, (c) 

 component matter of the organ- 

 ism, or (d) waste, meaning chem- 

 ical compounds incapable of 

 yielding energy with economic 

 profit by further splitting.) 



densities of population, over the range 

 from 5 to 100 inclusive, produce no sig- 

 nificant effect whatever upon duration of 

 life. The mean duration of life in hours 

 is approximately the same, about 44 hours 

 for male flies, and roughly 10 per cent 

 higher for female flies, at all densities, 

 and for both wild type and vestigial flies. 



INHERENT VITALITY 



From the point of view of theoretical 

 biology the condition of complete starva- 

 tion is an interesting one. It means that 

 we are observing the physiological be- 

 havior of the organism in pure form, so to 

 speak. This is evident from the following 



a charged Leyden jar. This concept has 

 nothing whatever to do with vitalism, but 

 is, on the contrary, purely mechanistic. 



The results depicted in figure 7 show 

 that the difference between normal wild 

 type flies and vestigial flies in respect of 

 duration of life, which under normal 

 conditions of feeding (that is, when it is 

 the expression of the total vitality im- 

 plicit in the normal A + B physiological 

 economy) follows the Mendelian law of 

 inheritance, is not dependent upon a funda- 

 mental difference between these two kinds 

 of flies in inherent vitality. This differ- 

 ence, on the contrary, appears merely to be 

 due to the fact that under the environ- 



