W. J. V. OSTERHOUT 3 



If we consider the behavior of the current from this point of view, 

 it is evident that in the simplest cases, where the plant is a membrane 

 only one cell thick (as in Porphyra and Monostroma) and the current 

 passes through this membrane at right angles to its surface, we need 

 consider only a single cell and its adjacent cell wall, as shown in 

 Fig. \, A. The part of the current which goes through the proto- 

 plasm may be designated as Cp. while that which traverses the cell 

 may be called Cw 



Experiments show that the resistance of the living tissue is much 

 greater than that of tissue which has been carefully killed with all 

 possible precautions to prevent any alteration of the cell wall.® 

 We therefore feel confident that the conductivity of the living proto- 

 plasm is less than that of the cell wall. 



A 



B 



Fig. 1. 



In order to see how the current may distribute itself let us suppose 

 the protoplasm to be replaced by a wire,^ P, as in Fig. 1, B and the 

 cell wall to be replaced by a wire, W. The current flowing between 



« Cf. Osterhout, W. J. V., /. Gen. Physiol., 1919, i, 299. J. Biol. Chetn., 1918, 

 xxxvi, 485. 



"^ We might consider the protoplasm to be replaced by two wires one of which 

 corresponds to the thin layers ofprotoplasm which are traversed by the current in 

 a direction at right angles to their planes, the other corresponding to the similar 

 layers of protoplasm in each cell (around the edges of the cell shown in Fig. 1, A) 

 in which the current flows in the plane of the layer. It is evident, however, 

 that these latter may be neglected in our calculations since they occupy such 

 exceedingly small fractions of the cross-section, 



j^ If we neglect these we may say that in traversing a cell the current passes 

 through a thin layer of cell wall and then one of protoplasm (in both cases at 

 right angles to the plane of the layer), then through the cell sap, and finally 

 through a layer of cell wall and one of protoplasm (at right angles to their 

 planes). It is evident that in this case we may neglect the effect of the cell 

 wall and of the cell sap since their resistance is very small in comparison with 



