1918] 
BONNS—ETHERIZATION AND ENZYME ACTIVITY 257 
tion for such different reactions. The permeability changes 
in the plasma membrane produced by narcotics involve dif- 
ferences in ion concentration on the two sides of the mem- 
brane, with resulting differences in electrical potential. It 
may be assumed that the cations concerned in the produc- 
tion of this potential are the ions derived from dissociation 
of carbonic and other weak acids produced in metabolism, and 
that carbonic acid is the chief electrolyte concerned in the 
production of this potential. In other words, the plasma mem- 
brane of the resting cell may be regarded as the seat of a 
potential difference and is electrically polarized in such a way 
that the solution in contact with its outer face is positive with 
respect to the enclosed protoplasm and that during stimula- 
tion this potential difference increases. If this Nernst 
theory of cell polarization is accepted, any increase in the 
ionic permeability of the membrane produces a correspond- 
ing change in its polarization; the phenomena involved in 
such electrical changes are hence primarily responsible for 
stimulation. 
Lillie points out that the most evident chemical effect of 
muscle stimulation is increased carbon dioxide production, 
and his explanation of this increase,—which may be applied 
to plant tissues,—is that it is due to the increased permeability 
of stimulation. Chemical equilibrium, it is recognized, de- 
pends upon equalization in velocity of the opposite pairs of 
chemical reactions. If the reaction products of one side of 
the equation are removed, acceleration results. If such 
products are slowly but continuously removed the relative 
velocity of the reaction producing them will depend upon 
the rate of such removal; any increase in this rate of removal 
from a system of interacting compounds in an approximate 
equilibrium will result in a corresponding acceleration of the 
process in the direction of the removed substance. 
Now, according to Lillie’s view, carbon dioxide is the reac- 
tion product whose rate of removal from the cell determines 
the velocity of the chemical processes concerned in stimula- 
tion. Normally the rate of removal is controlled by the de- 
gree of permeability of the plasma membrane. A slight in- 
