234 Walter Stiles and Ingvar Jorgensen. 
Also it should be noted that the electrolytic effect is much 
reduced when very small currents are used. As it is possible to 
measure currents of the order of 10' 14 amperes, the use of such low 
direct currents might be possible for some determinations. 
But the use of an alternating current is much to be preferred. 
By introducing and elaborating the method of using alternating 
currents in the determination of electrolytic resistances Kolrausch 
rendered a great service to physical science. His method is so well 
o 2 s s 
TfME IN MINUTES 
Fig. 1. For explanation see text. 
known as to need no description here; descriptions are to he found 
in many physical text-books. This is the method that has been 
almost exclusively used in the case of conductivity measurements of 
sap-extracts and of other liquids outside the plant, and is no doubt 
quite satisfactory for the purpose. 
In the case of living tissues, however, Kohlrausch’s method is 
unsuitable for several reasons. In the first place, as Kohlrausch 
himself points out, it is necessary to have electrodes of a certain 
size. Indeed the area of surface of the electrodes is an important 
