Human Red Cell Instability and Senescence 223 



content of the red cell, after treatment with alumina, suggests 

 that no alteration in the internal composition takes place. If, 

 however, the lost volume is simply that which was occupied 

 by the detached components, it is possible to calculate the 

 concentration of these components in the detached layer. The 

 results suggest that the concentration of the removable 

 layer is equivalent to that of a 2 per cent lipoprotein gel. 

 This agrees well with the value suggested by Mitchison (1953), 

 based on birefringence measurements, for the concentration 

 of lipoprotein in whole membrane. Ponder (1954), however, 

 suggests that the membrane is much less hydrated than this 

 and gives an estimate of 33 per cent for the concentration of 

 membrane material from observations of the volume of 

 fragmented ghosts. 



It seems worth considering the possibility that the concen- 

 tration of membrane components is not constant throughout 

 its thickness but increases radially inwards from the surface. 

 This could explain the ease of detachment of the tenuous surface 

 layers, and to some extent resolve the discrepancies between 

 the estimates of the membrane thickness and composition. 



The classical view of the structure of the red blood cell 

 membrane implies a framework of stroma protein surrounded 

 by a bimolecular layer of lipids, with a sprinkling of antigenic 

 protein at the surface. It seems unlikely that a cell possessing 

 such a structure could lose a substantial part of its membrane 

 and still remain intact. Among the recent views upon the 

 architecture of the red blood cell, that of Moskowitz and 

 Calvin (1952) agrees best with the experimental results above. 

 They envisage a membrane composed principally of fibrils of a 

 lipoprotein, elenin, orientated parallel to the cell surface and 

 cemented together by ether-soluble lipids. 



If the structure of the red cell membrane suggested by 

 Moskowitz and Calvin is accepted, then the physical dissolu- 

 tion of red cells might proceed as follows : when the cells are 

 suspended in a fresh saline medium the surface lipids will 

 dissolve or disperse in the medium ; the lipoprotein which was 

 held in position by the lipids will then become detached and 



