724 RALPH §S. LILLIE 
a cell of the dimensions of an Arbacia egg (0.072 mm.) ; the nucleus 
is omitted from consideration to bring the conditions to their 
greatest possible simplicity. If the original surface potential- 
difference in the resting cell A be placed at the probable value of 
0.1 volt, and it be assumed to fall suddenly to 0.05 volt as a result 
of increased ionic permeability (fig. 2, B), there will temporarily 
exist a potential-difference of 0.05 volt between the surface- 
layer and the interior of the cell; the gradient between the center 
and the periphery, a distance of 0.036 mm., will be ca. 14 volts 
| Potential 
Uniform 
A 
Fig. 2. A illustrates the conditions during the resting state. The plasma 
membrane is the seat of a potential-difference of ca. 0.1 volt with outer surface 
positive. The cytoplasm, within the double layer, is isoelectric, 7.e., the poten- 
tial is uniform throughout. In B the membrane is supposed to have undergone 
decided and sudden increase in ionic permeability so that the surface polarization 
is diminished by 0.05 volt. Ions are then free to travel to equalize the potential- 
difference, and a gradient exists at first between superficial and central regions 
as represented. The fall of potential over this distance 0.036 mm. will at first be 
0.05 volt, i.e., ca. 14 volts per centimeter. 
per centimeter. If we take the nuclear membrane also into con- 
sideration and assume an equal increase in permeability to occur 
simultaneously in both, the consequences will be essentially the 
same except that two oppositely oriented electrical fields will 
arise temporarily in the space between the membranes. It is 
to be noted that the regions most remote from the membranes 
will retain their original negativity longest. There will thus be 
a region of greatest negativity intermediate between the two mem- 
branes; from this region the potential will rise on either side toward 
has been passing, for a certain time after the polarizing current has been broken. 
The same phenomenon, as is well known, is shown by living tissues, as muscle or 
nerve; dead tissues show it to a relatively slight degree. 
