PHYSIOLOGY: S. TASHIRO 
111 
elusive enough to show that the carbon dioxide given off by an isolated 
nerve is produced by life processes. Experimental conditions, to their 
minds, might have caused the tissue to decompose in a manner quite 
different from its normal behavior. 
Further experiments show the following facts: 
1. If the sciatic nerve is removed from a frog, it shows an electrical 
response for many hours. Since electrical changes are characteristic 
only of living nerves, we consider that the isolated nerve does not die 
for many hours. If measurements are made on an isolated nerve at 
successive time intervals, we find that carbon dioxide production steadily 
decreases as the nerve approaches death The point of minimum car- 
bon dioxide production corresponds nearly to the point where electrical 
response ceases. The dead nerve gives almost no carbon dioxide. 
2. Although the nerve remains active for some time without oxygen, 
it is a known fact that absence of oxygen diminishes the excitability of 
the nerve. The carbon dioxide production of a nerve fiber is much 
less in hydrogen than in atmospheric air. We should expect that there 
would be no difference under these two conditions if the carbon dioxide 
production of an isolated nerve fiber were due entirely to the death 
process. 
3. The normal, uncut fiber in the body is very susceptible to many 
chemical reagents. A weak concentration of an anesthetic, for in- 
stance, renders the nerve nore excitable, or stimulates it, while a higher 
concentration makes it unexcitable. These reagents show similar effects 
on the carbon dioxide production of the cut nerve. 
These facts, to my mind, indicate that the production of carbon 
dioxide from an isolated nerve fiber is at least a correct expression of 
what is going on in the normal nerve in the body, and indicate clearly 
that the normal nerve must have a chemical activity which is accelerated 
when the nerve is stimulated. 
If the chemical activity is so vigorous as our results indicate, one 
naturally asks how we can explain the fact that the nerve impulse can 
pass continuously for hours without any measurable sign of fatigue. 
Apparent lack of fatigability in the nerve is a remarkable fact, but I 
wonder whether we should be willing to ignore the presence of metabolic 
activity in the contracting wings of insects which can fly continuously 
for hours at a rate of as high as three hundred vibrations per second. 
The ordinary induction coil we use for fatigue experiments, by the 
way, maintains not more than one hundred vibrations per second, at 
the maximum. 
