714 RALPH S. LILLIE 
such potential-differences. Granting that they exist, the radia- 
ting and spindle-shaped disposition of the colloidal material in 
the cell is readily understood, for colloidal particles in an elec- 
trical field must be affected similarly to other polarizable particles, 
and dispose themselves end to end along the lines of force, analo- 
gously to iron filings in a magnetic field. I propose to show that 
on the assumptions (1) that each semi-permeable membrane in 
the cell (nuclear membrane and plasma-membrane) is the seat 
of a potential-difference due to unequal permeability to anions and 
cations, and (2) that this potential-difference depends on the semi- 
permeable condition of the membrane and diminishes or disap- 
pears with marked increase in ionic permeability, it is possible 
to account for the existence of electrical fields within the cell 
having the characteristics requisite to produce the observed 
effects. All that will be attempted in the following pages, in 
fact, is to apply the membrane-theory of bioelectric processes to 
the case of the dividing cell. 
This theory, which originated in a suggestion of Ostwald?4 
and was first applied in detail to the bioelectric phenomena by 
Bernstein,2> who has been followed by Briinings, Hober, and 
others,?° is briefly as follows. In general any membrane, differ- 
ing in its permeability to ions of opposite sign, and interposed 
between two electrolytic solutions of dissimilar concentration 
(or composition), must be the seat of a potential-difference; i.e., 
the two surfaces will have different potentials due to separation 
of oppositely charged ions at the membrane, since the more pen- 
etrating ion will traverse the membrane more freely and impart 
its charge to the layer of solution in contact with the opposite 
face. Such a potential-difference will persist so long as the in- 
equality of concentration and of permeability to the two sets of 
ions remains unchanged. Equalization of the concentration- 
difference, as by gradual diffusion, will abolish the potential- 
difference; alteration in the permeability of the membrane, so 
24 Ostwald: Zeitschrift fiir physikalische Chemie, 1890, vol. 6, p. 71. 
25 Bernstein: Archiv fiir die gesammte Physiologie, 1902, vol. 92, p. 521. 
26 Briinings: Archiv fiir die gesammte Physiologie, 1903, vol. 98, p. 241, and vol. 
100, p. 367; Héber: Archiv fiir die gesammte Physiologie, 1904, vol. 101, p. 607, 
also Physikalische Chemie der Zelle und der Gewebe; further references here. 
