542 
PHYSIOLOGY: W. O. FENN 
1. The maximum is higher in pure CaCl2 than in mixtures of CaCl2 
and NaCl. 
2. The maximum is reached slightly sooner (or at a slightly lower 
concentration) in pure CaCl2 than in mixtures of CaCl2 with NaCI. 
3. There is a slight lag at the start of the NaCl curve in both Lami- 
naria and gelatine. In the case of gelatine, this lag appears only if more 
NaOH is put into the gelatine at the start than in the experiment 
recorded in figure S. With sufficient NaOH, the lag may be magnified 
into a distinct rise. This is in agreement with the fact, that NaCl will 
antagonize both anions and cations. The lag in the Laminaria experi- 
ments is seen in the fact that the velocity constant of the loss of resist- 
ance in NaCl is lov/est at the start. ^ 
The NaCl curve falls more slowly in figure 2 than in figure 1 but this 
may be paralleled by the results with Rhodymenia and other plants 
where the NaCl curve falls slowly. 
4. The final increase in conductivity (or of alcohol) in the mixtures 
of NaCl and CaClo is less rapid than in either of them taken separately. 
In general, the greater the percent of CaCl2 in the mixture, the less rapid 
is the increase. 
In the Laminaria experiments the curves approach a death point 
where the conductivity of the protoplasm is the same as that of sea 
water. No further increase of conductivity is possible. Of course 
this behavior would not be expected in gelatine. 
In a recent article in Science, Spaeth^ has presented a colloid-chemical 
theory of the Vital equilibrium' of protoplasm as an explanation of 
Osterhout's Laminaria experiments. Spaeth's theory differs from that 
outlined above in the following fundamental points. 
1. According to Spaeth the ^vital equilibrium' is between liquefying 
agents like NaCl and precipitating agents like CaCl2. Reasoning from 
the gelatine analog}^ the equilibrium is simply between positive and 
negative ions. 
2. Spaeth supposes that CaCl2 and similar electrolytes increase the 
viscosity of the protoplasm by an irreversible coagulation, after which 
the viscosity becomes that of the dispersion medium, due to the com- 
plete separation of the two phases. According to the gelatine experi- 
ments, on the other hand, low concentrations of Ca cause a perfectly 
reversible precipitate, or increase of aggregation, of an isoelectric nature, 
which disappears gradually with excess of CaCl2. Irreversible changes 
resulting in death appear only in much higher concentrations of CaCl2. 
It should be noted that the viscosity of a colloid (a conception which 
Spaeth uses extensively in his theory) is not a simple property of a 
