SALT EFFECTS IN BACTEEIAL GROWTH 513 



any organism does. The effects of salts should therefore not 

 only be very marked but might reach magnitudes that ought to 

 be taken into account in the culture of bacteria. 



Brooks (1919) found that NaCl and KCl in concentrations of 

 0.15 to 0.20M increased the rate of respiration of B. subtilis, 

 while in higher concentrations they decreased the rate. CaCl2 

 increased the rate in a concentration of 0.05M and decreased 

 the rate in higher concentrations. Deahng with the respiration 

 of Aspergillus niger, Gustafson (1919) likewise found a stimu- 

 lation by NaCl in concentrations of 0.25 to 0.5M and by 0.5M 

 CaCl.. 



The work of Winslow and Falk (1919) shows that NaCl and 

 CaClo both increase the mortality of Bad. coli in water. In 

 the case of NaCl 5 isotonic was distinctly lethal, while in the 

 case of CaCl2 0.1 isotonic was injurious. 



Greaves (1916) found the toxicity of anions as measured by 

 ammonification in soils to be in the following order: Cl> N03> 

 S04> CO3. He also noted that the toxicity of some salts in- 

 creases more rapidly with increased concentration than does 

 that of others. This action he ascribes to the physiological 

 factor of the organism rather than to the osmotic pressure or 

 salt action of the solution. 



The influence of alkaline salts upon phagocytosis was found 

 by Radsma (1920) to depend mainly upon the anions but also 

 somewhat upon the cations. Radsma explains the effect as 

 surface action and considers it an indication of colloidal chemical 

 structure of protein substances at the surface. 



Mathews (1906) pointed out that the action of salts upon the 

 protoplasmic system is due chiefly to the ions of the salts and he 

 considers the physiological action dependent upon the available 

 potential energy. 



Whether or not the salt action upon bacteria is due to the 

 available potential energy of the ions we shall not attempt to 

 decide. We merely wish to point out in this paper that salts 

 do affect bacterial growth much in the same m.anner as they 

 affect chemical reactions, coagulation, permeability, etc.,- that 



