314 



Scientific Proceedings (123). 



It appears then that the toxic effect of CaCl 2 reported in our 

 first experiments is an indirect one and is exerted only in an alka- 

 line solution in which it interferes with the regulative action 

 exerted by bacterial cells upon the reaction of a water or NaCl 

 solution. 



142 (1889) 



Studies on salt action. V. The influence of various salts upon 



bacterial growth. 



By C.-E. A. WINSLOW and MARGARET HOTCHKISS. 



[From the Department of Public Health, Yale School of Medicine, 

 New Haven, Conn.] 



Previous studies on salt action conducted in this laboratory 

 have dealt with the effect of certain mineral salts upon the death 

 rate of bacteria in water suspension. 1 The present investigation 

 relates to the influence of various salts upon growth in a one per 

 cent, pepton solution. The pepton used contained about 4 per 

 cent, ash and the solution had a reaction of Ph 6.8-7.0. The 

 salts studied were added in the form of chlorides in varying con- 

 centration. The solutions were inoculated with Bad. communis 

 and incubated at 37 0 C, the rate of growth being determined by 

 comparing the turbidity produced with standard suspensions of 

 dead bacterial cells. Check determinations by the plate method 

 indicated the substantial accuracy of this procedure. 



Twenty-three salts in all were studied and the limiting toxicity 

 determined as indicated below. 



The results in general confirm those reported by Matthews 2 

 for Fundulus, and Eisenberg 3 for bacteria; and it is evident, as 

 the former author pointed out, that there is a rough general rela- 

 tionship between toxicity and solution tension. We are making 

 a further analysis of the relation between the toxic action of these 

 salts and their other physico-chemical properties. 



The new point brought out in our studies is the general occur- 

 rence of a definitely stimulating action, exerted by concentrations 

 of salts below the inhibitive level. In the case of 15 out of the 



1 Winslow and Falk, Proc. Soc. Exp. Biol., 1922, xix, 311. 



J Am. Jour. Physiol., 1904, x, 290. 



■ Centr. f. Bakt., Abth. I, 1918, lxxxii, 69. 



