Human Red Cell Instability and Senescence 217 



as a relatively slow process, but at cellular dimensions it can 

 proceed with considerable rapidity. This is illustrated by a 

 calculation (Ponder, 1948) showing that 90 per cent of the 

 haemoglobin of a red cell can diffuse in four seconds through a 

 hole occupying only one thirty-thousandth of the cell area. 



In comparison with the information available concerning 

 the metabolism of various types of living cell, little is known 

 of the spontaneous diffusion processes to which they are con- 

 tinuously subjected. One exception, however, is the red blood 

 cell; it is well established that its internal contents are not 

 in thermostatic equilibrium with the environment but are 

 maintained at a steady level by active processes. While some 

 of the structural components and the haemoglobin are appa- 

 rently inert (Muir, Neuberger and Perrone, 1952), it has been 

 shown that the cell lipids are in a condition of rapid turnover 

 both by metabolism (Muir, Perrone and Popjak, 1951 ; Altman, 

 1953), and by passive diffusion (Gould, 1951). The integrity 

 of the red cell depends upon the presence of the lipids, and 

 since these substances are free to diffuse away, then to some 

 extent the cell itself can be regarded as a steady state system 

 maintained intact by its metabolic activity. 



This information, together with the knowledge that the 

 normal life-span of the red cell is known with considerable 

 precision and the fact that it is particularly convenient for 

 experimental purposes, decided the choice of this cell for the 

 investigation of its physical stability, even though it was real- 

 ized that the red blood cell is highly specialized and cannot be 

 considered representative of living tissue. 



This paper describes some experiments on the diffusion of 

 components from the red cell and its ensuing dissolution. 

 A detailed account of the experimental material and methods 

 is described elsewhere (Lovelock, 1955a). The loss of sub- 

 stance was accelerated by suspending the cells in a medium 

 maintained unsaturated with respect to the components of the 

 cell membrane. This was achieved either by repeated washing 

 or by including in the medium a neutral adsorbent substance, 

 namely alumina. A few observations are also included on the 



