184 GEORGE RALPH MINES. 



amount of surface presented by them, and the electric charge they 

 carry. At present this cannot be done in any quantitative sense, yet 

 we may illustrate from material already available the nature of the 

 biological interest which will accrue from knowledge of this kind. 



In the first place, new light is thrown on the relations between the 

 living heart muscle and its normal environment. 



We have considered the importance of the P+ of the solution. 



H 

 Take now the case of magnesium. Mg • • is the only simple divalent 

 ion which can be expected to act on the heart simply qua divalent ion. 

 As we have shown, Ca ' ", Sr'", and Ba * ' enter probably into 

 special chemical relation with some constituent of the tissue, while 

 the other metals which give divalent ions (such as beryllium, zinc, 

 cadmium, etc.) form solutions which are hydrolyzed.* 



It is generally stated that an emulsoid colloid is very insensitive to 

 salts. This is not true, at any rate in the case of some typical €;mul- 

 soids, when simple trivalent ions are considered. Quite small con- 

 centrations of the rare earth solutions can produce large effects on 

 colloidal materials which present all the other characters of emulsoids. 

 Many experiments on a variety of colloidal solutions lead me to the 

 conclusion that a fairer statement of the characteristic relations 

 between emulsoid colloids and electrolytes would be this : that as 

 compared with the suspensoids there is a very great difference in the 

 relative concentrations of simple di- and tri-valent ions needed to 

 produce the same effect. While for suspensoids the ratio of the 

 activities of di- to tri-valent ions is taken ordinarily as of the order 

 of 3 to 100, for emulsoids it is rather of the order of 1 to 10,000. 

 It is certain that these ratios vary widely with different colloids, and 

 that from a more precise study of these ratios than has at present been 

 undertaken much more will be learnt about the colloids themselves, 

 but the broad distinction appears to hold. 



On the artificial scheme of membranes, then, magnesium produces 

 effects tending in the same direction as those produced by the simple 

 trivalent ions and by the hydrogen ion, but is enormously less potent 

 than these. 



Precisely the same is true of the action of Mg * " on the heart. 



* Incidentally it should be noted that the effect of hydrolysis, as regards the activity 

 of the solution on the heart and on colloids such as gelatine, is precisely opposite in the 

 case of these solutions of divalent ions from that described for trivalent ions. For the 

 H ions, though less powerful than the equivalent concentration of simple trivalent ions, 

 are much more powerful than the equivalent concentration of divalent ions in these rela- 

 tions. Consequently a solution of beryllium, which is hydrolyzed, affects the heart, and 

 colloid systems of the class sensitive to H", much more powerfully than the non-hydrolyzed 

 solutions of magnesium. 



