166 INJURY, RECOVERY, AND DEATH 



ism, as shown by the electrical resistance, is greater in 

 NaCl + CaCla than in NaCl + HCL^** 



The hypothesis was further tested by investigations 

 on other salts, the most interesting of which are those 

 which (in contrast to those just mentioned) are more 

 effective than CaCla in decreasing permeability, such as 

 La (N03)3, Ce (N03)3, etc. Here also it was found that 

 the degree of antagonistic action could be foretold by 

 observing the amount of decrease of permeability pro- 

 duced by the pure salts. The results of these investiga- 

 tions afford strong support to the hypothesis. 



The soundness of this point of view is indicated not 

 only by the fact that we are able to predict both qualita- 

 tively (and to a considerable extent quantitatively) the 

 effect of combinations of salts*° but also by the very 



" See page 140. 



" It should be noted that mixing solutions of two salts which belong 

 to different classes does not produce an effect which is merely intermediate 

 between the two. For example, tissue may be killed by an exposure of 

 24 hours to NaCl or to CaCU, but not in a mixture of these in the proper 

 proportions. 



The writer has found cases in which two substances which can decrease 

 permeability are able to antagonize each other. So far as the writer's 

 experiments with Laminaria have gone there is no great amount of 

 antagonism in such cases and what there is may perhaps be correlated 

 with the fact that all substances which decrease permeability do not act 

 alike, some producing a, much greater decrease than others. Moreover 

 these substances will, if the exposure be suificiently prolonged, alter their 

 action and increase permeability. The rapidity of this change varies 

 with different substances, and this may be related to the fact that some 

 of these substances antagonize each other to some degree. 



Experiments on some plants (in which the criterion of antagonism is 

 not electrical resistance, but growth) show a fairly strong antagonism 

 between magnesium and calcium. It is possible that for these plants mag- 

 nesium belongs in the first class. 



It will be noted that the hypothesis, as here set forth, says nothing 

 about the mutual relations of substances belonging to the same class, but 

 merely states that substances of one class will antagonize those of the 

 other. In this form the hypothesis is completely justified by all the 

 experiments, including those on organic substances. 



