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BIOLOGY: A. J. LOTKA 
Proc. N. A. S. 
proportionality factor is here determined strictly by the particular mechan- 
ism employed. 
Reflection shows that all transformations of money or of economic 
assets of any kind into energy by exchange upon the market are of this 
character. It is always a case of trigger action. Somewhere there is a 
store of available energy, which can be tapped with an expenditure of 
greater or less effort. The payment of the price sets in motion the requi- 
site machinery for the release of that energy (or for its transfer of ownership, 
the release being delayed at the discretion of the buyer) . 
In view of the entire absence of any general law regulating the ratio of 
energy released to energy applied in such case of trigger action, we may 
ask the question, how does it come about that economic conversion factors, 
economic ratios-in-exchange of different forms of energy, display any 
regularity whatever? 
We have been accustomed, in thermodynamics, to disregard mechanism. 
In dealing with energy conversions by trigger action we must make a 
complete change of attitude. Here everything depends on mechanism. 
If we find any degree of regularity in the conversion factors, this must be 
due to regularities in the mechanism, i.e., in the human organism, and 
its social aggregations; and we cannot hope to make any progress in our 
understanding of the physical principles involved except by taking due 
account of the mechanism. 
In view of the extreme complexity of the systems in which economic 
phenomena have their course, it may appear hopeless to attempt analysis. 
But reflection shows that the complexity is in the details ; the broad under- 
lying features resolve themselves into comparatively simple lines. 
Our vital interest in physical energy arises out of the following facts: 
1. The body of a living organism is not in equilibrium with its sur- 
roundings. In other words, the living body (and also the dead body, for 
some time after death, as popularly conceived), in its natural environment, 
is a source of available energy. 
2. Though not in equilibrium with its surroundings, the living body 
is in an approximately steady state ; furthermore, it is one of the essential 
conditions for the continuance of life that this approximately steady state 
be maintained. Extreme departures therefrom result in permanent dis- 
placement from the steady state, and, ultimately, in the dissipation of 
the available energy presented in the substance of the organism. 
3. In the course of events a certain amount of available energy, varying 
according to the nature of the organism, is unavoidably dissipated, per 
unit of time. 
It follows that every organism, in order to maintain the steady state 
necessary for its survival, must be provided with devices for capturing 
available energy. 
