Stiles and J ergensen.— Studies in Permeability. IV. 61 
a 3 m. solution of methyl alcohol. The curves show how, as a result of the 
increased permeability produced by increased concentration, the maximum 
value of the exosmosis is reached sooner with increasing concentration. 
Although the curves are only given for the first 24 hours, measurements 
were made over a considerably longer period. The following table shows 
that eventually complete exosmosis of electrolytes takes place even with 
considerably weaker solutions than 2 m., which, according to Czapek, is the 
limiting concentration above which exosmosis takes place and below which 
it does not : 
Concentration Conductivity after 
of solution. 
2 hrs. 
4 hrs. 
12 hrs. 
24 hrs. 
48 hrs. 
8 m. 
466 
5 2 5 
‘ 
6 m. 
450 
5 l6 
538 
4 m. 
430 
552 
562 
2 m. 
194 
464 
570 
570 
1*5 m. 
33 
90 
30 7 
509 
m. 
20 
38 
82 
156 
390 
o -75 m. 
16 
29 
59 
no 
37 ° 
Distilled water 
10 
21 
50 
79 
141 
The above table shows that it is impossible to speak of a critical 
concentration required to produce exosmosis of the cell contents. The rate 
of exosmosis, indeed, depends on the concentration, but diffusion out 
from the cell takes place in all concentrations. Czapek’s value of 
T i per cent, by volume (about 2 m.) as the critical concentration required to 
produce exosmosis is therefore meaningless. A different result is obtained 
by Czapek’s method according to the time one supposes is required to 
produce equilibrium conditions. Even with distilled water, exosmosis 
continues slowly until bacterial action sets in and measurements no longer 
have reference to the simple action between potato tissue and water. So 
that by assuming equilibrium to be established after any selected time, any 
desired value can be obtained as a value of the critical concentration 
required to produce any particular amount of exosmosis. 
But one matter exhibited by Czapek is confirmed in this investigation, 
which is that any member of the homologous series of primary alcohols has 
a greater effect on exosmosis than a lower member of the series in the same 
concentration. 
Thus experiments made with normal propyl alcohol show that this 
alcohol in o-6 m. concentration is equivalent in regard to its action in 
producing exosmosis to ethyl alcohol of 1*3 m. concentration. The general 
course of events is exactly similar to that with the two lower alcohols. 
The accompanying curves (Fig. 7) show the exosmosis during the first 
24 hours for concentrations of normal propyl alcohol from 0*4 m. to m. It 
should be noted, however, that in the case of the 0*4 m. solution, the 
maximum exosmosis was approached after 48 hours, although from an 
inspection of the curves for the first 24 hours this differed little from that 
