122 M. M. McCooL 



is an essential mineral nutrient it is extremely' injurious when there is no 

 calcium in the culture solution, the presence of calcium in sufficient amount 

 entirely preventing the toxic action of magnesium. 



Loew regarded the toxic action as due to the displacement of calcium by 

 magnesium in certain parts of the protoplast, with a consequent loss of 

 function. Moreover, if sufficient quantities of calcium salts are placed at 

 the disposition of the plant thus affected, then, in accordance with the law 

 of mass action, the magnesium is again replaced by calcium and the normal 

 equilibrium is restored. There is here a clear enunciation of the physio- 

 logical balancing of magnesium by calcium. Loew appears to have been 

 unaware of the earlier work on antagonistic action, in which certain 

 phj'siological processes of animals or their effects on animal life were 

 under investigation. However, since Loew studied plants, and since he 

 developed one of the most important of the antagonistic relations - — that 

 between calcium and magnesimxi — his work may be made the startmg 

 point in this study. 



Extensive data have been presented since 1899 concerning the antago- 

 nistic action of different bases with respect to both animals and plants. 

 The work of Loew, Kearney, Loeb, Harter, Osterhout, and others has 

 developed many facts respecting this phenomenon in general. It has been 

 satisfactorily demonstrated that a solution of any one nutrient mineral 

 base at some concentration below the limits of osmotic influence is com- 

 monly poisonous. (Some plants are apparently uninjured by calcium 

 chlorid at concentrations approaching the point of plasmolysis.) Further- 

 more, this poisonous action, or toxicity, can be more or less completely 

 counteracted, sometimes by one base but especially by such a combination 

 of salts as enters into a balanced nutrient solution. 



It will be the purpose of a later paper to summarize the data on the 

 relative toxicity of the different bases, and to present some additional 

 facts. The present discussion is confined to the question of the extent and 

 significance of antitoxic action between certain bases. Further studies 

 on this subject with some of the more toxic metals will also be reported 

 later. 



The work of Loew (1892 a), above referred to, established in an incontro- 

 vertible manner the antagonistic action of calcium and magnesium, but 

 from this there are afforded no special indications that further antidotal 

 relations may exist between other mineral bases. Indeed, Loew subse- 



