218 INJURY, RECOVERY, AND DEATH 



a wire, W. The current flowing between the points X and 

 Y in the wire P may be called Cp ; that in the other wire Cw. 

 The total current, C, flowing between X and Y will be the 

 sum of the partial currents, or, 



C=CP + CW 



We may consider the current (conductance) as equal to 

 the reciprocal of the resistance and write 



- = - +- 

 R Rp Rw 



in which R is the total resistance between X and Y, Rp is 



'W 



A B 



Fig. 93 



the resistance of the wire P, and Rw , that of W. Apply- 

 ing this equation to Laminaria 31 (and expressing the 

 resistance in the usual way as the per cent, of the normal) 

 we may calculate the values of Cw, CP, Rw, and Rp. 



Under normal conditions in sea water, the resistance 

 is taken as 100 and therefore C = l-r- 100, but in certain 



81 So far we have considered only the simplest case, when the plant is 

 only one cell thick. But it is evident that these considerations also 

 apply when several membranes are placed together, forming a mass 

 comparable to the tissue of Laminaria. The only difference is in that 

 case the current would traverse a very thin layer of cell wall in passing 

 from one protoplasmic mass to the next, so that what we have spoken 

 of as the resistance of the protoplasm would be composed in part of 

 the resistance of these cell walls. When the protoplasm is dead the 

 total resistance is only 10.29 and the resistance of these cell walls must 

 be only a small fraction of this. Consequently their resistance in the 

 living tissue of Laminaria is undoubtedly less than 1 when that of the 

 protoplasm is 140. The resistance of these cell walls may therefore 

 be neglected. 



