EXCITATION AND CONDUCTION 71 
algebraic sum of these results might readily approximate 
the value found for normal respiration. 
The general phenomena are the same for ethyl 
urethane, except that the primary increase of the gas 
in light narcosis is much more marked, being more 
than twice as great if compared with the value for the 
normal nerve at 20°2 C. It was noted that the nerves 
after treatment with a 1 per cent urethane solution were 
hyper-irritable, but a part of this large increase must 
doubtless be due to the higher temperature at which 
the experiment was performed. 
Carbon dioxide production from “‘inexcitable”’ normal 
nerve-—During the warm weather we occasionally came 
across a claw-nerve preparation in which no sort of stimu- 
lation of the nerve could evoke any response whatever, 
although the peripheral organs were perfectly excitable. 
Response by the attached muscle to stimulation of the 
claw nerve of the spider crab is of three sorts: con- 
traction, or relaxation of the claw, and movements of the 
lower joint. In general, different strengths of the 
stimulating current result in different responses. It was 
at first thought possible that in these cases the stimula- 
tion might be calling forth opposed responses, so that 
one neutralized the other, and thus that no response 
resulted. But further investigation showed apparently 
that the nerve was inexcitable, since after immersion 
in the sea-water irritability was often restored. To 
whatever cause this may have been due, the interesting 
fact is that such “‘inexcitable’’ nerves invariably showed 
an abnormally low rate of carbon dioxide production. 
The results of the quantitative estimates on these nerves 
are given in Tables VII and VIII, horizontal column 2. 
