468 L. V. HEILBRUNN. 



Finally it should be pointed out that the experiments of Loeb 

 (17) apparently indicate an increase in the permeability of 

 Fundulus eggs to water in the presence of various anesthetics. 



It is not my purpose to claim that in anesthesia there is no 

 decrease in the permeability of the cell to salts or to water. 

 Perhaps eventually this may be found to be a constant occurrence. 

 But it seems at least premature to conclude a decreased per- 

 meability from the slight and uncertain evidence hitherto 

 presented. Only by closing our eyes to the experiments that 

 show the opposite of a decrease and only by neglecting the 

 numerous sources of error which have scarcely been considered 

 by previous experimenters, is it possible to consider the per- 

 meability evidence as convincing. 



Even should we, some time in the future, find it true that 

 anesthesia is always associated with decreased permeability of 

 the plasma membrane of the cell, we would not be very much 

 closer to an understanding of how and why the anesthetic stops 

 cell activity. Permeability is a surface phenomenon, the activity 

 of the cell goes on largely in the interior. Thus even if we 

 accept the permeability doctrine, we must postulate a secondary 

 hypothesis to explain how the permeability effect is transferred 

 to the interior of the cell. 



Many years before the permeability doctrine was thought of, 

 various physiologists held the idea that anesthetics affected the 

 colloidal condition of the protoplasm in one way or another. 

 For a long time this idea remained a mere speculation, but in 

 recent years it has been definitely shown that anesthetics do 

 have a very real effect on the colloidal state, or at any rate 

 upon the viscosity of the protoplasm. Both in plant and animal 

 cells it has been shown that dilute solutions of ether cause a 

 liquefaction of the protoplasm, and that more concentrated 

 solutions cause a coagulation. There is a remarkable corre- 

 spondence between widely different sorts of living substance. 

 However in plants only those concentrations of ether which cause 

 coagulation prevent the rotary movement of the protoplasm. 

 This was therefore regarded by Heilbronn (18) as the anesthetic 

 concentration. In animal cells on the other hand it was found 

 that concentrations which caused liquefaction prevented cell- 



