PROTOPLASMIC STRUCTURE 123 



A and B. When the capacities of the condensers are 

 the same and the resistances of the two halves of the 

 circuit (on either side of the bridge) are the same (or 



when their ratios are equal; i.e., when ~ = -^^] no 



current passes through the detector; but if the capacity 

 of one condenser (A) is changed, the current passes until 

 the capacity of the other (B) is made the same. Now 

 the capacity of a condenser is increased if a conducting 

 layer is introduced into the dielectric between the 

 plates, and to a degree which is proportional to the con- 

 ductivity of the layer. Hober's method, therefore, 

 consists in introducing between the plates of one of the 

 condensers (B), after the system has been brought into a 

 balanced condition, a glass vessel containing a suspension 

 of living cells (blood corpuscles) in isotonic sugar solution. 

 Such a suspension does not conduct electricity (in the 

 usual Kohlrausch sense), yet it increases the capacity 

 of the condenser and so allows a current to flow across 

 the bridge. This result shows that the suspension con- 

 tains an electrically conducting fluid; this can only .be 

 in the interior of the cell, since the suspension-medium 

 is sugar solution, which is a non-conductor. The 

 addition of saponin (which destroys the membrane and 

 increases the Kohlrausch conductivity) was found not 

 to change the capacity, indicating that the conductivity 

 of the cell-contents is the same whether the semi- 

 permeable membrane is present or not. If a glass vessel 

 containing a salt solution is placed between the condenser 

 plates, a similar increase of capacity is shown; and by 

 comparing the effects produced by salt solutions of 

 known conductivity with those produced by suspensions 



