THE INJURY CURRENT OF NERVE 
337 
In the second place, the results obtained by the immersion of nerves in hydro- 
chloric acid (page 309) strongly reinforce such a line of argument. In that instance 
the widest range of effects, from extreme increase to extreme decrease of the injury 
current, was obtained by the use of a set of solutions all much more dilute than the 
' isotonic ' solution. All these solutions practically formed ' vacua ' into which the 
electrolytes of the nerve diffused with great rapidity, the limit to the extent being 
determined by the time of immersion and being practically the same in each case. 
In this case the effect of the error is not obvious, because it is always maximal 
and the same in the results of every solution used. It is not obvious until the actual 
quantities in the ' concentration law ' for hydrochloric acid solution is examined. 
Ew 1 ■ 1 
= Io g- 
Ea n 
The value of k in this example is minimal. One of the reasons which contributes 
to this diminution is the factor capable of definite anticipation, namely, the dilution 
of the ' internal solution ' of the nerve by rapid diffusion processes. 
The form of the ' concentration law ' is always the same ; conclusions deducible 
from its form, such as the possibility of reversing the direction of the injury current 
are, therefore, inevitable. The actual value of the constant ' k ' which it contains 
E« . k 
Ea to n 
is the same for a very great range of concentrations, and is only varied by con- 
ditions which change permanently the value of the source of the injury current. 
The meaning of this value ' k ' is fixed by the form of the law, when k = n the injury 
current vanishes ; ' k ' therefore is the concentration of the solution, an immersion in which 
will reduce the value of the injury source to zero, and necessarily is different for different 
conditions of the nerve. 
The particular value of 'k,' which is of the greatest interest, is the value which is 
true for the effects of immersion in solutions which produce the least permanent effect 
upon the conditions of the nerve, that is for the value obtained by experiments with 
solutions as near the ' isotonic ' solution in concentration as possible. The range of 
concentration, which is suggested as being most worthy of accurate experiment, is 
from one-fifth to one-tenth gramme molecule per litre of the chloride solutions 
which have been examined. 
From this point of view the following series of experiments with one-eighth 
gramme molecule KC1 seem worthy of especial attention. 
In order that the real quantitative value of these results may be of permanent 
interest, they also are given as they were taken in succession, and are given, without 
exception, from a series of experiments performed one after another in the course of 
three days. It will be seen that the initial values are greater than usual, a fact which 
