Accumulators of Specific Nervous Energy 293 
another and of decomposing again, and in dynamic 
equilibrium among themselves. (It may be remarked 
here that the expression “dynamic equilibrium” of a cir- 
culatory system is always to be understood in the sense 
of inalterability for the time in the conditions of move- 
ment at each point of the system. Thus, for example, 
the system of distribution of the drinking water of a city, 
which is fed from a given constant number of reservoirs, 
whose head of water is maintained always at the same 
height, and in which a given constant number of water 
taps are always open, will settle in a short time into a 
dynamic equilibrium in our sense, and continue in it so 
long as the accession of a new reservoir, for example, or 
the opening of other water taps does not cause the transi- 
tion to a new dynamic equilibrium. ). 
As soon as the discharge of this nervous accumulator 
occurs, which can produce thus only a single definite 
specificity of current, and which can discharge itself upon 
only a single fixed point, it will necessarily effect a single 
very definite change in the dynamic equilibrium of this 
given circulatory system. And in the cases in which this 
change of the dynamic equilibrium requires the doing of 
a certain amount of work, this required expenditure of 
work or energy will be very definite for each discharge, 
and can be provided only by the accumulator itself. Con- 
sequently, in order that the discharge may take place, this 
quantity will have to be less than, or at most equal to, 
that which the accumulator can actually furnish. 
But the quantity of work which each accumulator is 
capable of furnishing will necessarily be proportional to 
the mass of the substance which constitutes it. And 
since, as we saw, the resistance R which each accumulator 
with its current of definite specificity is able to surmount, 
