STUDIES ON EXOSMOSIS 
489 
The first effect of cerium chloride is, like that of calcium, an in- 
hibition of the exosmosis, but this effect is quickly reversed, and the 
rate of exosmosis becomes greater than that from any other of the 
lots of material. This is probably due to the not inconsiderable toxicity 
of the solution of cerium chloride, enough of which probably remained 
in the protoplasm to cause injury, with consequent greatly increased 
exosmosis. The effect of sodium chloride is only temporary, disap- 
pearing within one and one quarter hours after the removal of the 
tissue from the sodium chloride solution. 
Table 2. 
Effect of Salts on Exosmosis from Unleached Tissue 
Conductance in Ohms, X lo^, of Distilled Water in Contact with Tissues 
Distilled Water 
NaCl 0.22 M 
CaCl2 0,17 M 
CegCle 0.05 M 
Distilled Water 
0.50 
28.0 
44-5 
24.0 
8.0 
1.25 
41.0 
49-5 
27.0 
16.0 
3.00 
48.0 
51-5 
40.0 
26.0 
4-57 
51.0 
53-0 
45-5 
31.0 
5.90 
51.5 
53-3 
47.0 
32.0 
The data are given in Table 2, and are graphically presented in 
Figure 3, in which the ordinates represent the total gain in conductance 
at intervals of time after the end of the period of thirty minutes which 
was allowed for diffusion of salts from the intercellular material. 
A consideration of the fact that after the first thirty minutes the 
exosmosis from tissue which had been treated with calcium chloride 
was less than that from tissue which had not been in contact with 
any salt solution, shows that the substance causing the increase of 
conductance was not, or at least only to an extremely small extent, 
the salt used; the data therefor show that sodium salts increase, and 
calcium salts decrease the permeability of the protoplasm to substances 
other than themselves. 
By analogy with the experiments of Osterhout (3) on Laminaria 
it should be possible to find some mixture of salts which, in a solution 
of the proper concentration, would leave the permeability of the dan- 
delion protoplasm unaltered. Such a combination was found. It 
was not possible to determine exactly its optimum constitution; but a 
solution consisting of 80 parts sea water and 20 parts of a 0.52 M 
solution of calcium chloride, diluted to 21/52 of its original concen- 
