224 INJURY, RECOVERY, AND DEATH 



as follows : An electrical current passing through a liv- 

 ing plant flows partly through the cell wall and partly 

 through the protoplasm. The relative amounts of these 

 two portions of the current can be calculated. The 

 outcome of such calculations shows that the conclusions 

 drawn from the study of the resistance of the tissue as 

 a whole apply also to the resistance of the protoplasm, 

 and consequently to the permeability of the protoplasm 

 to ions. 



If these conclusions are sound it is evident that per- 

 meability may be measured with considerable accuracy. 

 Measurements under a variety of conditions indicate that 

 marked fluctuations of permeability are possible, and, 

 when their duration is brief, no permanent injury results. 

 It is obvious that the effect of such fluctuations on 

 metabolism may be of great importance. 



Some writers 37 seem to think that under normal con- 

 ditions the cell is quite impermeable to salts. This is at va- 

 riance with the results obtained from measurements of 

 permeability by the method outlined above. If the net 

 resistance of the tissue under normal circumstances is 

 taken as 100, we find that in certain solutions (having the 

 conductivity of sea water) it may rise to 300. The proto- 

 plasmic resistance under normal conditions may be taken 

 as 140. When the net resistance of the tissue rises to only 

 250, the protoplasmic resistance increases to 874.89, a gain 

 of 524.92%. 



It is therefore evident that the permeability of the cell 

 is by no means at a minimum under normal conditions. 

 This conclusion is borne out by the results of experiments 

 on plasmolysis 38 carried out by the writer as well as by 



87 Cf. Osterhout (1915, G). 



88 Cf. Osterhout (1913, B). 



