THE INJURY CURRENT OF NERVE 
By J. S. MACDONALD 
PREFACE 
IN justification of this attempt to secure a hearing for an already elaborately-handled 
theme, it may be pardonable to emphasize the importance of a very obvious fact, 
that the joint work of chemists and physicists has made the present time 
extremely opportune for the conduction and consideration of such research. 
It may be said that this phenomenon of the injury current was most exhaustively 
examined at a time when physical science was not ripe to deal with such possibilities, 
and that the physiologist was obliged at great inconvenience to grope for correlated 
physical data; whereas, at the present time, such a mass of the required information 
has been collected, codified, and arranged according to simple and sufficing 
explanatory hypotheses by the physicist, that physiological research of this kind can 
with great advantage be carried out upon easily anticipated lines. 
It may, on the other hand, be said that at the present date it is much more 
necessary to apologize for the carrying out of any study of electrical phenomena 
occurring in animal tissues, and especially such as are consequent upon injury, than 
to be imbued with a sense of their importance; for it is now realized that every 
process of diffusion occurring between solutions of electrolytes, such as solutions of 
inorganic salts, is a probable source of electrical phenomena, and also that every injury 
is necessarily succeeded by processes of diffusion following the destruction of pre- 
existing barriers. It is, for example, an absolutely certain prediction that differences 
of potential must be found between electrodes placed upon the external and internal 
surfaces of glandular organs, upon which it is an otherwise amply determined fact 
that solutions of inorganic salts are present differing in concentration or in nature in 
these two positions. And again, when it is otherwise known that stimulation of nerves 
leading to these structures causes a further difference to arise between the two 
solutions, it is certain that new differences of potential will arise as the result of such 
stimulation. In such cases it may seem doubtful whether the information gained 
from an examination of differences of potential can be of interest in comparison with 
the more direct information attainable by other means. 
