722 RAUPH-S. LiGLIEe 
difference at each surface will be the geometrical mean of that 
which either surface would show if the metal were in contact with 
only the one solution.4* The metal will necessarily be isoelec- 
tric, i.e., of the same potential in all its parts (outside of the 
double layer itself); this potential will be negative by a certain 
value (equal to 0.51 volts for zinc in contact with a normal solu- 
tion of zine sulphate) in relation to both solutions in contact 
with the metal. This corollary is especially important from the 
present point of view, because it means that the central enclosed 
solution is positive in relation to the metal enclosing it. 
Now the cell—considered from the electrochemical point of 
view as a system with two concentric semi-permeable membranes 
bounding a solution which in virtue of its slow oxidations is con- 
tinually freeing carbonic and other acids and hence H-ions—must 
exhibit conditions essentially similar to the above. The seat of 
these oxidations is the cytoplasm. The region enclosed by the 
nuclear membrane must thus represent a region of higher poten- 
tial than the adjacent cytoplasm, i.e., is positive relatively to 
the latter;° the same is true of the solution in contact with the 
surface of the cell. The persistence of such conditions depends 
on the semi-permeable character of the limiting layers or mem- 
cal concentration-cell would be the result, and zinc ions would be deposited from 
the stronger solution and pass into the weaker while anions simultaneously by dif- 
fused from the more to the less concentrated solution until the two were equalized. 
Impermeability to anions is the essential characteristic of the space separating 
the two solutions in the above system as also of the space bounded by the semi- 
permeable membranes in the cell. 
4 The grounds for this conclusion will be found in Michaélis’ treatment of the 
case of asolid substance in contact with its saturated solution; this case is analogous 
to the above inprinciple. Cf. Dynamik der Oberflichen, p. 57. 
46 Tt is evident that this view assumes that the H-ion concentration within the 
nuclear membrane is less than that outside, i.e., in the cytoplasm. Such a view 
implies that the oxidative metabolism in the resting cell—and hence the produc- 
tion of carbonic and other acids yielding the H-ions—is essentially confined to 
the cytoplasm. The conditions in active tissues like muscle support this concep- 
tion;in fact, the characteristic activities of cells are in general cytoplasmic 
activities; nuclei are relatively uniform in their characters. Hence the above 
assumption appears to be in accordance with the general facts of physiology. The 
question is difficult to decide by direct experiment, though possibly the use of 
indicators capable of penetrating both nucleus and cytoplasm without injurious 
action might yield valuable results. It should be borne in mind that oxygen, in 
order to reach the nucleus, must penetrate a layer of cytoplasm containing 
reducing substances. 
