THE INJURY CURRENT OF NERVE 
231 
In the figures given below, and in the case of all other experiments recorded in this section, the 
arrows indicate the order in which the observations were taken : — 
Distance of point from the 
Potential Diffe 
rence between this point 
anil the 
cross section 
cross section 
(a) 
(b) 
(0 
1 
centimetre 
■01904 
•014.16 
JJaniell 
J 
(*) 
2 
?? ... 
•01696 
■01624 
11 
(3) 
3 
?> ... 
•01696 
■01688 
(+) 
+ 
■01672 
> 
■01688 
(5) 
5 
... 
•01 520 
•01 520 
If the two sets of observations (a) and (b) of this experiment are taken singly, it 
is obvious that a different idea is capable of being formed from each of them of the 
distribution of potential upon the longitudinal surface. The maximum of the curve 
representing this distribution is in case (a) obviously to be placed between points 
(2) and (3), point (3) being the mid-point of the piece of nerve examined. The 
maximum in case (b) is to be placed between points (3) and (4) and, therefore, on the 
other side of the mid-point. The reason for this difference between the two sets of 
observations is readily seen from the fall in the potential difference which has taken 
place at point (1) in the time necessary to take the whole set of observations, a fall 
of -005 volt, that is of almost 25 per cent, of the initial value. The effect of this 
fall is not noticeable in the two observations at point (4) which rapidly followed upon 
one another ; in fact, there is apparently a slight increase, due probably to the 
selection of a slightly different point upon the return visit. The fall has nevertheless 
been taking place all the time, and, provided that it is regular and that the observa- 
tions have been taken at regular intervals, its effects can be eliminated by taking the 
average of such a set of observations ; for corrected values are then obtained, which are 
almost accurately those actually existent at the moment of ' mean time ' of the whole 
set of observations. 
Taking this set of average values from this experiment, we have : — 
Point (1) -01665 
„ (2) -01660 
» (3) -01697 
„ (4) -01680 
„ (5) -01520 
Daniell 
