ANTAGONISM 181 



is not the case. Only when it has proceeded a good way 

 toward the death point, does it become irreversible. On 

 the other hand, the fall in NaCl (due to liquefaction) 

 might be expected to be reversible at every stage. But it 

 ceases to be wholly reversible after it has proceeded 

 one sixth of the way (or less) to the death point. 



5. Since the changes in viscosity occur in dead as 

 well as in living tissue we should expect to find in both 

 cases similar changes in resistance. It is found that in 

 tissue which has been killed in such a manner as not to 

 alter the properties of the cell wall, the decrease in vis- 

 cosity in NaCl produces no appreciable effect on resis- 

 tance. Even when the process goes so far that the tissue 

 is reduced to a very soft jelly, there is little or no change 

 in resistance. 51 The hardening in CaCl 2 produces some 

 rise in resistance, but it is much too small to account 

 for the great changes which occur in living tissue. 



It might be supposed that the reason that no change 

 in resistance occurs in dead tissue is because the hard- 

 ening and softening do not proceed as far as in living 

 plants, but this is not the case. Moreover, it is found that 

 the decrease of viscosity in NaCl is accompanied by 

 absorption of water, while the increase of viscosity in 

 CaCl 2 is accompanied by loss of water, and these pro- 

 cesses take place in the same way in living and dead tissue. 



It would seem that these and other important objec- 

 tions must be removed before we can accept the idea that 

 changes in permeability are determined by changes 

 in viscosity. 52 



These objections apply to the theory advanced by 



81 In a liquid a change of viscosity alters the resistance, but this is 

 not necessarily the case in a gel. Where a gelatin gel is converted to 

 a sol, the change in resistance is very slight. 



M It would appear that the term viscosity is loosely applied to a variety 

 of phenomena which may be produced in different ways. 



