EFFECT OF IONS ON BACTERIA 107 



before the isotonic point is reached. Ions of the 

 phosphates favour cell development when the ionic 

 concentration is low, but retard it when the con- 

 centration is high. 



Upon micro-organisms their influence was studied 

 by Kronig and Paul*, who used specially the spores 

 of anthrax and Staphylococcus pyogenes aureus for 

 their experiments. These are of importance in con- 

 nexion with the subject of disinfection, and the 

 reader is referred to the original paper for a fuller 

 account of the observations of which a mere outline 

 can be given : 



1. The ions of Hg, Cu, Ag, Zn, Cd, Pb, and Au, 

 are all toxic. They are protein precipitators even 

 in the lowest concentration. The observers found 

 that the toxic action of salts of these metals upon 

 living vegetable cells stands in a definite relation to 

 the electrolytic dissociation. The action of the 

 metallic ion depended not only upon the specific 

 effect of the cation, but upon the ionic concentra- 

 tion and association with an anion. The halo- 

 gens Cl, Br and I, have a destructive effect which 

 decreases as their atomic weight increases. Not only 

 the halogen, but the cyanogen compounds of Hg 

 disinfect in proportion to their dissociation. The 

 disinfecting power of an aqueous solution of mer- 

 curic chloride is diminished by addition of HC1 or 

 another halogen compound, probably through the 

 recombination of ions. (An instance of the dissocia- 

 tion of one substance into ions and their recombina- 

 tion to form another substance is observed after 

 testing diabetic urine with Fehling's solution. If 



* Zeit.f. Hyg. und Infections!*., 1897, xxv., 112. 



