CHEMICAL SIGNS OF IRRITABILITY 39 
6.7X10 7g. for the same units. In other words, the 
output was increased between 100 and 200 per cent by 
the tetanization of the nerve. 
Electrical stimulation of medullated nerves.—The fact 
that the increased production of carbon dioxide on 
stimulation is not limited to the non-medullated nerve 
is shown by our quantitative determination on the 
sciatic nerve of the frog. Ten milligrams of frog’s nerve 
gave 14.2X1o0 ” g. of the gas during ten minutes of 
stimulation as compared with 5.5 X10’ g., the amount 
produced by the resting nerve of the same animal. Here 
again stimulation increased the output from 200 to 300 
per cent. 
Other stimulation—We have now established the 
fact that when a nerve is stimulated by an electrical 
current it gives off more carbon dioxide. In order to 
test whether this increased production of the gas on 
electrical stimulation is due to the direct decomposing 
influence of the current or to the state of excitation 
produced by the stimulus, many additional facts must 
be sought. In the first place, if the increased gas pro- 
duction is not due to a change in rate of metabolism, 
but to the current itself, then we should expect that 
the stimulation of a killed nerve ought also to cause more 
gas production, provided, of course, that we may assume 
that the conditions under which electrical decomposition 
takes place are the same in the living and in the dead. 
When we place two nerves killed by steam, one in each 
chamber of the biometer, and stimulate one of them, the 
stimulated nerve does not give off more carboh dioxide 
than the unstimulated when the same strength of current 
is employed as was used in the other experiments. 
