INORGANIC SALTS 169 



many others, where the foregoing relation of antagonism 

 to valence does not appear to hold, and especially in 

 those numerous cases where different cations similar in 

 valence have widely different antagonistic or other 

 physiological actions.^ In such cases the special chemical 

 properties of the compounds formed between the ions 

 and the structural colloids of the cell must apparently 

 be taken into consideration. Thus various facts indicate 

 that calcium proteinates or calcium soaps (or both) 

 are of special importance as constituents of cell structures; 

 and these compounds cannot be replaced satisfactorily 

 by the corresponding compounds of other bivalent 

 elements.^ Such a conception explains why strontium, 

 the metal most closely resembling calcium in general 

 chemical properties, usually comes nearest to calcium in 

 antagonistic effectiveness; the other alkali earth cations 

 come next; while the bivalent heavy metals are effect- 

 ive in only a few special cases (Mn. Co, Fe++), the great 

 majority of these metals being too strongly toxic to act 

 as efhcient antagonists.^ 



^ Cf. Hober's discussion in his recent papers on the physiological 

 action of calcium; Arch. ges. Physiol., CLXVI (191 7), 531, and 

 CLXXXII (1920), 104. 



2 The cases are numerous where calcium has a specific action which 

 cannot be replaced by that of other cations, even Sr; instances are the 

 specificity of calciimi in phagocytosis (Hamburger), in the inhibition 

 of swimming plates, and in the preservation "of contractility in heart- 

 strips. On the other hand, in its simple stabilizing or protective action, 

 (e.g., in cytolysis, etc.) Ca can often be replaced by other cations (cf. 

 Hober's papers, loc. cit.; cf. also Wiechmann, Arch. ges. Physiol., CXCV 

 [1922], 588). 



3 Nevertheless even the most toxic cations, like Ag and Hg, may 

 show definite antitoxic action in certain cases; e.g., the beat of the 

 ctenophore swimming plate in pure isotonic NaCl solution is prolonged 

 several times by AgNOj and HgCL in concentrations of m/ 100,000 to 

 m/ 200,000 (cf. American Journal of Physiology, XVI [1906], 117). 



