342 
THOMPSON YATES LABORATORIES REPORT 
From this fact and from the following considerations an attempt is made to 
deduce the conductivity of the internal solution. 
In the first place, it is assumed that an ' external solution ' of the conductivity 
of -745 grammes per cent. KC1 has been replaced by a similar bulk of a solution of 
1*490 per cent. KC1, an assumption which is justified by the regularity of the results 
obtained in the preceding section of this paper. 
In the second place, the alteration in weight is taken as too small to affect the 
result. 
It may, therefore, be considered that the following equations represent the con- 
ditions present : — 
The conductivity of the pre-existent 'external 
solution,' having the same specific con- 
ductivity as one-tenth normal solution of 
KC1. 
+ 
The conductivity of the internal solution. 
(1) The conductivity as 
measured before 
immersion. 
(2) The conductivity as 
measured after 
immersion. 
The conductivity of a solution of one-fifth 
normal KC1, having the same spatial 
distribution as the pre-existent 'external 
solution.' 
+ 
The conductivity of the internal solution. 
But these equations are simplified by the fact that the specific conductivities of 
one-tenth and one-fifth the normal KC1 solution are known and are to one another . 
practically as 1 is to 2. 
Therefore, 
(1) 527 = C e + Ci 
(2) 58-1 = 2 C c + Ci 
where C c is the conductivity of the ' external solution ' and C ; is the conductivity of 
the ' internal solution,' 
.*. by subtracting (1) trom (2) 
C c = 5'4 
That is to say, that the conductivity due to the pre-existent external solution is 
practically one-tenth of the total conductivity of the nerve. 
Js a corollary it follows that the conductivity of the axis cylinders accounts for nine- 
tenths of the total conductivity of the nerve. 
In the sciatic nerve of the cat only one-third of the total area of the nerve is taken 
up by the circular bundles of nerve fibres. This figure was obtained by casting the 
enlarged shadow of a cross section upon a screen, drawing over the shadow, cutting 
up and weighing the paper. 
