MEASUREMENTS OF ELECTRICAL CONDUCTIVITY 
The average resistance of the sciatic nerve of the cat is four thousand ohms 
per centimetre when given as based upon measurements of long stretches of nerve 
(five centimetres). The value of this statement (and it is of the orthodox character) 
is limited, in so far as it offers no basis for a real comparison of the resistance of the 
sciatic nerve with that of any other nerve of different average calibre, and also since 
it gives no information as to the varying nature of the resistances of the differing 
elements of structure entering into the composition of the nerve. 
The first limit is only to be surmounted by a determination of the calibre, and 
this is a matter of some difficulty when use is made of nerves from which subse- 
quently data of a different kind are to be sought, and which must not, therefore, be 
damaged in the process. 
In the present series of measurements, this difficulty has been avoided by the 
use of an indirect method, which does not injure the nerve, and which affords results 
that are certainly not more than 5 per cent, in error. 
The second limit it is not possible, for the present, to surmount, and the value 
of the information attainable is thereby greatly reduced. The reduction in value is 
not, however, so great as to leave the taking of these measurements merely an 'academic' 
interest ; since the information obtained, scanty though it be, is from one point of 
view of extreme value. The nerve, being a ' moist conductor,' owes its con- 
ductivity to the solutions of electrolytes which it contains, and measurements of 
conductivity, therefore, can be used as guides to a knowledge of the quantity of 
electrolytes present in solution in the nerve, although giving no guide as to their 
relative distribution in its component parts. The information so obtained is by no 
means perfect, but is of value, since the limits to its accuracy are not such as to 
render the errors introduced more than a fractional part, even if a large fraction, of 
the true value which they tend to conceal. 
The measurements, indeed, form the only means by which any approximate 
notion can be acquired of the total amount of electrolytes in solution, that is of the 
amount of matter which can partake in the production of the electromotive phenomena 
of the nerve ; and it is obvious that in a study of these electromotive phenomena it 
is desirable to decide, even if roughly, the proportion which this amount bears to that 
of the total matter in the nerve. 
Measurements 
The following data are taken from eleven separate experiments upon sciatic 
nerves obtained from eleven cats, from the bodies of which they were removed 
immediately after death. The measurements of resistance were made by an ordinary 
