1 68 PROTOPLASMIC ACTION AND NERVOUS ACTION 



structure (e.g., a cilium or plasma membrane) requires a 

 certain state of subdivision of the chief structural colloids. 

 Apparently in the normal medium, e.g., sea water, the 

 influence of the various ions is so balanced as to preserve 

 this state; the collective effect of the negative charges 

 carried by the anions (CI, SO4, HCO3, etc.) is just 

 balanced by the collective effect of the positive charges 

 carried by the cations (Na, K, Ca, Mg). In the pure 

 solution, however, of NaCl, in which no bivalent cations 

 are present, the influence of the anions is insufficiently 

 compensated, and the colloids are altered in a manner 

 injurious to cell structure: i.e., a preponderant influence 

 of anions is the essential toxic factor in such cases. The 

 addition of bivalent or trivalent' cations of any kind 

 has under these conditions a compensating and hence 

 antagonistic or antitoxic influence; trivalent ions exercise 

 this effect in much lower dilution than bivalent ions, 

 and bivalent than monovalent ions. At an appropriate 

 concentration, the balance is restored, protoplasmic 

 structure remains normal, and life continues. The 

 reverse condition, in which the toxic action of the pure 

 solution results from a prepotency of cation action, and 

 in which accordingly the addition of small quantities of 

 salts with powerfully acting anions has an antitoxic 

 effect, is apparently also realized in some cases; e.g., the 

 ciliated epithelium of the molluscan gill {Mitylus) in solu- 

 tions of SrCla; here various Na salts (NaOH, NaBr, NaT, 

 NaCNS, NaaSOj show well-marked antagonistic action.^ 

 Such purely physical explanations, while apparently 

 partly applicable in some cases, prove inadequate in 



^ Cf. American Journal of Physiology, XVII (1906), 89; cf. p. 129; 

 cf. Raber, Jour. Gen. Physiol., II (1920), 541, for analogous observations 

 on Laminaria. 



