336 Prof. W. M. Thornton. [Jan. 12, 



Table II — continued. 





Ohms, per 1 







Fresh milk, 1 to 2 lirs. after milking... 



233 





240 

 252 



] ■ 



^•From different sources. 





252 







557 







480 







210 





Milk with slight acid reaction 



196 







180 







169 







1400 







1300 







1250 





Comparing Tables I and II, it will be seen that B. typhosits from gelatine 

 has practically the same conductivity as the culture medium, and that that 

 on agar, though at first high, falls even below that of the medium, suggesting 

 that there is marked absorption of conducting salts by organisms grown 

 on agar. . 



3. Influence of Sub-culturing on Conductivity. 

 It was recognised from the above figures that, to obtain perfect comparison 

 of the conductivities of various organisms, they should be taken from 

 cultures, not only of the same age, but of the same order of sub-culture. An 

 organism which has been many times sub-cultured could not in general be 

 expected to have quite the same conductivity as one fresh from' the animal. 

 The following determinations were made to decide this point. The organism 

 used was B. coli communis from house sewage, and the cultures were all in 

 broth from the same stock : — 



Ohms per cm. cube. 



Fresh from the animal 95—90 



First sub-culture 60 



Second „ ! 45—40 



Third „ 1 40 



Fourth „ 35 



Fifth „ ! 35 



Sixth „ ! 35 



Seventh , ! 35 



There is, therefore, a rapid increase in conductivity due to the change of 

 habitat from the body to broth. After the fourth sub-culture a steady state 



