102 THE THEORY OF IONS 



ethylic compounds of lead, zinc or mercury. Even 

 in therapeutics advantage is sometimes taken of 

 such ester-like combinations. 



There is still another way in which the specific 

 effects of many ions can be increased or decreased, 

 viz. through the combination of one ion with another. 

 This occurs when ions of the alkaline earths act upon 

 protein in the presence of alkali metals. The pre- 

 cipitation of protein which can be brought about by 

 the alkaline earths may be inhibited through the 

 addition of alkali metals, or hastened through addi- 

 tion of the anions, the most powerful of which are the 

 sulphocyanates. Indeed there seems to be a physio- 

 logical antagonism between the monovalent cations 

 Na, K, NH 4 , Li, and the divalent cations Ca, Ba, Sr, 

 etc. ; as well as a synergistic increased effect of the 

 anions in the presence of calcium, barium and stron- 

 tium. This physiological antagonism has already 

 been noted in Loeb's experiments with ions upon the 

 development of the eggs of Fundulus magellus, a 

 small bony fish, upon the contraction of the swim- 

 ming bell of medusae and upon ciliary movement. 

 There is a marked difference in the electrical charge 

 carried by the monovalent and divalent ions, and 

 this may be taken in part as explanatory of the 

 antagonism between them. 



The relationship of calcium, barium and strontium 

 to the proteins is important, because of the position 

 occupied by calcium in physiology and pathology. 

 They occupy a position between the alkali metals 

 and the true heavy metals. In common with the 

 former they have a high precipitating power ; in 

 common with the latter they form a firm bond 



