Role of Salts in Preservation of Life 181 



Wasteneys and I could show that the rate of the absorption 

 of acid by the fish is the same in solutions with and without salt. 

 This proves that the action of the salts consisted in this case 

 not in preventing the diffusion or absorption of the acid, but in 

 modifying the deleterious effect of the absorbed acid. 



We can state a little more definitely the cause of death by 

 acid. If we put the fish into a weak acid solution in distilled 

 water just strong enough to kill the fish in from one to two hours 

 (e.g., 500 c.c. H2O+2.O c.c. n/10 HCl), we notice that the acid 

 very soon makes the normally transparent epidermis of the 

 fish opaque, and a little later the epidermis falls off in pieces 

 and shreds. This, however, is probably not the direct cause 

 of the death, but I am inclined to assume that the fish die 

 from suffocation caused by a similar action of the acid upon 

 the gills. 



The action of the acid upon the epidermis of the body as 

 well as upon the gills is prevented through the addition of 

 neutral salts. 



It is well known that the action of acids upon proteins can 

 be inhibited by neutral salts.' Thus the internal friction of 

 certain protein solutions is increased by acids while the addition 

 of neutral salts inhibits this effect (Pauli). The swelling of 

 gelatin caused by acid is inhibited by salts (Procter). ^ 



It is possible that in the experiments with acid the fish is 

 killed in the following way. The acid causes certain proteins 

 in the surface layer of the epithelial cells of the gills and of the 

 skin to swell, whereby this surface layer becomes more perme- 

 able for the acid. The acid can now diffuse into the epithelial 

 cells and act on the protoplasm, whereby the cells are killed. 

 If salts are present in the right concentration, the combined 

 action of acid and salt causes a dehydration of the surface film 



1 It seems that the first experiments on the antagonism between acids and 

 salts were published by the author in PflUgers Archiv, Vol. LXXV, p. 308, 1899. 



2 The beautiful osmometric experiments ol E. LUlie should also be mentioned 

 'in this connection. 



