ELECTROLYTES IN LIVING MATTER 73 



tion. I think we may take it for granted that, at least, K forms a 

 nondissociable constituent of the protoplasm of a number of tissues of 

 animals and plants, and that it therefore may be considered a building 

 stone for living matter in the same sense as the above-mentioned anions. 



This fact explains the so-called ohgodynamic effects. This term 

 was applied to the fact that certain heavy metals hke Cu, or, as I behave, 

 traces of their salts, can produce a toxic effect. Obviously the Cu-ions 

 form upon their entrance into the cell undissociable or practically 

 undissociable compounds with protein substances, and thus their con- 

 centration is kept lower in the cell than in the surrounding solution. 

 The consequence is that in due length of time enough Cu may diffuse 

 into the cell to act toxically. There is therefore no reason why we 

 should continue to set aside the ohgodynamic effects as a distinct group 

 of phenomena in biology. It is quite possible that an ion may be 

 utilized in two ways by a tissue; namely, for the synthesis of mole- 

 cules from which it can no longer be dissociated as an ion, and in the 

 form of salts, — possibly ion-proteids, — where the metal can disso- 

 ciate as an ion. 



What is true for the K may also be true for the Mg, but it can 

 scarcely be so for the Zn in Rauhn's solution, although, curiously enough, 

 it is not so much less important for Aspergillus than K. Raulin found 

 that if he allowed spores to develop on the above-mentioned solution, 

 which contained all fourteen constituents, except K, the crop was only 

 one twenty-fifth of the dry weight of that which he got when he added 

 K. When the trace of Zn contained in that solution was omitted, 

 the dry weight of the crop was only one tenth of that which he obtained 

 when Zn was added. Raulin has made similar determinations for all 

 the constituents of his nutritive solution. The figure following each sub- 

 stance in the table below expresses how many times greater the dry weight 

 of the crop was with the addition of the substance than without it. 



NH, 153 



PO4 182 



Mg 91 



K 25 



SO, 25 



Zn' 10 



Fe . 2.7 



SiOj 1.4 



It was to be expected that the omission of NH, from the solution would 

 reduce the crop considerably (to ^^-g- of its weight), inasmuch as it 



