216 J. E. Lovelock 



temperature ovarian tissue may also fail to survive even one 

 week, although under otherwise similar conditions it survived 

 a year or more at —190° (Parkes and Smith, 1953). The 

 survival of red blood cells at — 20° is poor compared with that 

 at —78°, although at both temperatures glycolysis has slowed 

 to a point where there is a negligible consumption of glucose 

 during the survival of the cells (Chaplin et ah, 1954). 



The notion that the cessation of activity would lead to 

 the suspension of vital processes assumes not only that the 

 harmful effects of wear and tear result directly from activity, 

 but also that the cell is stable in a physical sense in the absence 

 of activity. 



Nowadays it is more usual to regard living cells as dynamic 

 entities. It is thought that their contents, and possibly also 

 their structures, are maintained at a constant level by a 

 balance between the accretion of synthesis and the losses due 

 to chemical change and to passive diffusion. If a cell, which 

 is in dynamic equilibrium at its normal temperature, is cooled 

 to a temperature where metabolism ceases, or is greatly 

 slowed, it will continue to suffer the loss and disorientation of 

 its components by random molecular movement and by dif- 

 fusion, for these physical processes are only slightly affected 

 by a fall in temperature. It follows that the life-span of a cell, 

 which is normally in dynamic equilibrium, will be short if it is 

 stored at a temperature where the balance between synthesis 

 and diffusion is no longer on the credit side. It may well be 

 significant that the successful cold storage of living cells has so 

 far only been achieved under conditions where diffusion itself 

 is greatly slowed, namely at very low temperatures, in the 

 presence of viscous substances such as glycerol, or in the dry 

 state. 



The concept of the living cell as a steady state system is 

 helpful not only in emphasizing the inadequacies of the purely 

 mechanistic approach to the manifestations of entropy, but also 

 in suggesting the more probable nature of the wear and tear 

 process suffered by the cell, namely, the loss and disorienta- 

 tion of its substance by diffusion. Diffusion is usually regarded 



