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PHYSIOLOGY: S. TASHIRO 
ON THE NATURE OF THE NERVE IMPULSE 
By Shiro Tashiro 
HULL BIOCHEMICAL LABORATORY. UNIVERSITY OF CHICAGO 
Read before the Academy, December 9, 1914. Received January 13, 1915 
The nerve fiber, as is well known, shows not only the highest degree 
of irritability, but also possesses power to transmit a state of excita- 
tion in the most efficient manner. Our interest in the study of the nerve 
impulse Hes not only in the fact that the nervous system is one of the 
most important factors in all organic activities in the higher animals, 
but also, in the fact that it constitutes the center of a general problem 
that deals with the mechanism by which a living substance adjusts it- 
self to its environment. 
In order to study the nature of the nerve impulse, many physiologists 
have investigated what takes place in the nerve fiber during the con- 
duction of the impulse. The results were very peculiar: there were 
no structural changes of any kind, no heat production, and there ap- 
peared to be no production of carbon dioxide, nor did they find any 
change in the distribution of the organic materials in the tissue. When 
electrical changes were discovered in the stimulated nerve, the problem 
was considered to be settled once for all. The idea that the nerve im- 
pulse is of an electrical nature was, however, soon doubted, when Helm- 
holtz observed that the velocity of the nerve impulse is of an entirely 
different magnitude from that of an electrical current. One thing 
seemed to be certain : that the nerve impulse can pass through the fiber 
without consuming any material. The fact that we can not detect fatiga- 
bility in the nerve after continuous stimulation supported the belief that 
certain quickly reversible physical conditions exist in the nerve, and 
that changes in these conditions must determine the phenomena of 
excitability and conductivity in the nerve. Such changes were thought 
to be either of the colloidal state, of the surface tension, or of the per- 
meability of the nerve. 
With the new apparatus which measures as little carbon dioxide as 
one ten-millionth gram, we have demonstrated that an isolated nerve 
fiber gives off a definite amount of carbon dioxide and that when it is 
stimulated this carbon dioxide production is more than doubled. These 
facts not only indicate that there is another kind of functional change 
beside the electrical, but also show that the chemical changes in the 
nerve fiber are of the same magnitude as those of other organs. 
To some physiologists, however, our results do not seem to be con- 
