34 Discussion 



Davson : That would be a most dangerous conclusion to draw. If your 

 chloride space altered under experimental conditions, it could very well 

 be due to penetration of chloride into the cells. 



Wallace : We have been working with tissues for some time from the 

 standpoint of hydrogen ion gradients between cells and extracellular 

 fluid. I have often discussed this work with investigators interested in 

 single cells and the events that occur within the cell. One often finds that 

 such workers are unwilling to accept the interpretations derived from 

 analytical values for whole tissues. They point out that the interior of the 

 cell is not homogeneous. Potassium and sodium do not appear to be 

 evenly distributed and the hydrogen ion concentration seems to vary 

 from locus to locus. I am certainly not ready to give up the study of 

 ions and their distribution in tissues, but I think one must always bear in 

 mind that membrane equilibria can only tell a part of the story. The 

 concept of the cell, particularly the muscle cell, as an "empty bag" 

 cannot be completely accepted. 



Davson : In general I am in favour of your iconoclastic approach, but 

 you are basing most of your argument on the findings of the electron 

 microscopists and they are by no means above criticism themselves. They 

 are working on fixed tissue and talk about their endoplasmic reticulum. 

 It certainly appears as a most complicated system of canals, but one 

 wonders how real it is. Is one to abandon all hope of applying rather 

 elementary physical chemistry to our problems just because of these 

 complexities? We think of the cell as being bounded by a limiting mem- 

 brane with certain permeability characteristics. The electron micro- 

 scopists show us the membrane which does exist, but then they find little 

 holes or vesicles just next door to it. They say that what is happening is 

 that the membrane is opening up, the vesicle is coming in and they have 

 caughtit just as it was coming in. It may well be that they are right. We 

 have obviously got to be suspicious of treating things too simply — there 

 you are absolutely right. On the other hand, I am not willing to stop 

 applying elementary physical chemistry to problems of salt transfer just 

 because of these complexities. 



Adolph : I should like to add something to the point about swelling and 

 shrinking with the accompanying transfers of electrolytes. When tissue 

 slices, not only kidney slices but also liver slices, and two tissues which 

 we did not have to slice, i.e. diaphragm and auricle, are transferred from 

 low temperature to high, or from anoxic media to oxygen, they shrink. 

 This shrinking in high temperature and oxygen is fully reversible any 

 number of times; for instance, in ten-minute periods, in low temperature 

 or in high, in nitrogen and in oxygen, we can get complete reversibility of 

 the swelling and shrinking (Adolph, E. F., and Richmond, J. (1956). 

 Amer. J. Physiol., 187, 437). This indicates that there is no permanent 

 damage to these tissues from the swelling and shrinking, and it also indi- 

 cates that the transfers are very rapid. It looks as though, if there is 

 electrolyte transfer, it is as rapid as that of water. But I am not con- 

 vinced that the electrolyte transfers are necessary for this swelling and 

 shrinking. We have no method of measuring the speed of the electrolyte 

 transfers, but we have a method of measuring that of the water transfers. 



