PHYSICO-CHEMICAL PROPERTIES. 93 



to touch upon the relation of the alkaline earths to the 

 proteins. 



The protein precipitates produced through the action 

 of the alkaline earths are irreversible in so far as the solu- 

 tion of a precipitate that has once been produced is 

 difficult and scarcely leads to the restitution of an un- 

 changed protein. The effects of calcium, strontium, and 

 barium are determined to a large extent through the 

 presence of other ions simultaneously present. Under 

 these circumstances the effects of the ions of a salt of 

 an alkali metal also antagonize each other, only in a way 

 opposite to that observed in precipitations produced 

 through pure neutral salts. The formation of a pre- 

 cipitate in a solution of native protein through the alkaline 

 earths is favored by anions and inhibited by cations. The 

 anions under these circumstances arrange themselves 

 in the following order, in which the most powerful pre- 

 cipitants come first: 



Acetate, chloride, nitrate, bromide, iodide, sulphocyanate. 



The cations arrange themselves in the following order 

 in which the greatest inhibitor of precipitation is put 

 first: 



Magnesium, ammonium, potassium, sodium. 



Nothing stands against the assumption that it is the 

 protein constituents of protoplasm that constitute the point 

 of attack of the ions in the organism, and this belief 

 cannot only be supported by experiment, but is also of 

 heuristic value. 



The two chief laws of protein precipitation, the additive 

 and the antagonistic effects of ions, hold also for the 

 physiological properties of ions. All cations, for example, 

 have certain physiological characteristics in common, in 



