INORGANIC SALTS 167 



on the whole most effectively by comparing the action of 

 salts on colloidal solutions and emulsions with their 

 action on living cells.' The physiological effects pro- 

 duced by salts and salt combinations vary with the nature 

 of the ions in a manner which in many cases shows a 

 close parallelism with the physical effects produced by 

 the same salts in simple colloidal systems. For example, 

 in the counteraction of the toxic effects of pure Na salt 

 solutions the results all indicate that the cation of the 

 antagonistic salt is the effective agent; and in this case 

 certain relations highly characteristic of the action of 

 ions on colloidal systems are shown clearly; thus with 

 the cilia of Arenicola all salts of bivalent heavy metals 

 (Co, Ni, Cd, Zn, Mn, Pb, Fe++, Cu) were found to pro- 

 duce their maximal antitoxic effects in concentrations of 

 the order m/400 to m/i6oo; while with trivalent metals 

 (Al, Cr, Fe^'O the physiologically corresponding concen- 

 trations were from 50 to 100 times less.^ This increase 

 in effectiveness with increase in valence is characteristic 

 of the action of salts on negatively charged suspensoid 

 systems (rule of Schulze and Hardy); and apparently 

 the observations above indicate that the cations produce 

 their effects in the living system by influencing the state 

 of subdivision of the suspensoid colloids forming part 

 of the protoplasmic structure. Other cases of rapid 

 increase in physiological effectiveness with increase of 

 valence are well known. 



Such cases of antagonism are consistent with the hy- 

 pothesis that the normal state of the living protoplasmic 



^ Cf. Hober's review in his textbook, chap, x, p. 471. 



^American Journal of Physiology, VII (1904), 419; similar results 

 were obtained with the giU cilia of Mitylus: ibid., XVII (1906), 89. 



