PHYSIOLOGY: W, O. FENN 
541 
RESISTANCE 
Decrease of Alcohol 
m%- 
40%- 
8ITZ- 
140%- 
„Jkath..p.Qint. __TlZ:r:rT:rz? 
w 
25 
~5oh(m 
flfj ^-^i^} ooncentmtion--^ 
FIG. 1. 
FIG. 2. 
FIG. 1 
Curves from Osterhout's experiments showing the changes in the electrical conductivity 
of protoplasm when discs of Laminaria are transfered from sea water to NaCl 0.52M or 
to CaCl2 0.27 8M or to mixtures of the two (all having the same conductivity as sea water.) 
Ordinates represent per cent of resistance (t he resistance of the discs in sea water being 
taken as 100%). When the resistance has fallen to 10% of the control, the death point is 
reached. Here the protoplasm has the same conductivity as sea water. 
Curves showing how the effects of NaCl and CaCl2 on the electrical resistance of pro- 
toplasm may be imitated by the effects of NaCl and CaCl2 on the alcohol precipitability 
of gelatine (containing NaOH 0.005M). The ordinates represent the decrease (8 minus 
the number of cc.) of 95% alcohol required to produce an opaque precipitate, the abscissae 
salt concentrations. For comparison with Laminaria it is assumed that the salts diffuse 
into the gelatin (as into the protoplasm of Laminaria) CaCl2 diffusing 80% as fast as NaCl. 
The molecular concentration of the NaCl solution is twice as great as that of the CaCl2 
solution (which is approximately the case in the Laminaria experiments). At the end of a 
given time, when the concentration of CaCU in the gelatin is 0.031M, the concentration of 
NaCl will be 0.031 X 2 X (100 -~ 80) = 0.078M. This point is indicated in the figure. 
The concentrations in mixtures at this point can easily be calculated (e.g., in NaCl 50% + 
CaCla 50% they would be half of those just mentioned). 
It is therefore evident that we may regard the abscissae as representing time as well as 
concentration and that from this point of view the figure becomes comparable with figure 
4, showing the changes in alcohol precipitabiHty and in resistance which would be expected 
to occur with time if the salts were diffusing into the gelatin. 
The last point on each curve is obtained by interpolation between the preceding point 
and a later one not shown in the diagram. 
FIG. 2 
