Stiles and j0rgensen. — Studies in Permeability . V. 425 
These results are shown graphically in Fig. 6. They show clearly the 
effect of increasing quantities of sodium chloride in the external solution in 
producing a progressive decrease in swelling until above a certain concentra- 
tion shrinkage is produced. 
It will be observed how, after a certain time, the swelling or shrinkage 
reaches a position of approximate equilibrium which is maintained for at 
least sixteen hours. On the de Vriesian view this indicates that the sodium 
chloride does not enter the tissue in any quantity. For if it did enter the 
cell it would either alter the permeability or it would not. In the latter 
case, since the substances dissolved inside the cell cannot pass out, the 
osmotic pressure inside would be raised, and, when the concentration of 
sodium chloride inside and outside was the same, the tissue should ulti- 
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Time in hours. 
F ig. 6. Curves illustrating the 
absorption and excretion of water 
from potato in sodium chloride 
solutions of various concentrations. 
Fig. 7. Curves illustrating the 
absorption and excretion of water 
from potato in sucrose solutions of 
various concentrations. 
mately swell to the same extent as in distilled water. Similarly, if the 
permeability to the substances inside the cell were decreased, there would 
still be swelling as in distilled water. On the other hand, if the permeability 
were increased so that dissolved substances inside the cell diffused out, one 
would expect increased swelling, at first due to the increase in salt concen- 
tration inside the tissue, followed by a shrinkage as the permeability in- 
creased and the internal solutes diffused out. This is not indicated by the 
curves obtained with sodium chloride, although such is indeed the course of 
events observed with some substances which for other reasons we know 
bring about an increase of permeability. 
N 
It will be noted that with these samples of potato a solution of ^ 
sodium chloride was approximately isotonic on the osmotic hypothesis with 
the cell sap. 
