Entropic Contributions to Mortality and Aging 



327 



is a part of the general theory of absolute rate processes, and is also the object 

 of a great deal of experimental work, particularly on proteins. It is discussed 

 in another paper in this volume (12). 



It has been suggested by a number of investigators that the rate of aging 

 is a function of the level of metabolic activity. In evidence of this is the relation 



m 

 < 



(r 

 > 



< 



o 



o 

 o 



_i 

 o 



en 



>- 



X 



a. 



-2 



2 4 6 8 10 12 



PHYSIOLOGICAL VARIABLE X 



Fig. 2. Interpretation of the probability distribution of fluctuation and of the 

 lethal bound in terms of a potential which is a function of the physiologic state 

 variables (6). The solid curves are the isopotential contours. The dashed 

 line L'-L" is the lethal hound. This is the highest point ('divide') on the potential 

 surface in any direction from the steady state, O. Different parts of the lethal 

 bound can be at different potentials. If the potential is markedly lower in one 

 part of the divide, most escapes will occur through this pass. Such preferential 

 directions of escape may be identified with the occurrence of specific disease 

 conditions. The contour lines are isopotential contours of the potential function 



E = a^x" — biX^ + a^y^ — biV^ 



A stochastic mortality process has already been investigated for the one- 

 dimensional case of the cubic potential (6). 



between metabolic rate (or body size) and life expectation among the Mammalia, 

 and the dependence of life expectation on environmental temperature in cold- 

 blooded forms. However, the relation is not a simple one. Birds, with body 

 temperatures as much as 5°C higher than mammals (13), tend to have life 



