EXCITATION AND CONDUCTION 67 
in osmotic pressure, but that the lowering of carbon 
dioxide output cannot result essentially from the osmotic 
effect is evidenced in many indirect ways. We found 
that the sciatic nerve of the frog when treated with 2 per 
cent ethyl urethane solution gains about 30 per cent in 
weight during ten minutes’ immersion. No change in 
weight, however, takes place in the spider crab’s nerve 
on a similar treatment with the same concentration of 
this narcotic. Loss of irritability ensues in each case, 
and in each case the carbon dioxide production is greatly 
diminished. A 4 per cent solution of chloral hydrate 
causes the spider crab’s nerve to increase So per cent 
in weight in ten minutes, while 4 per cent ethyl urethane 
solution produces no change of weight in the same nerve. 
Yet both narcotics depress carbon dioxide output 
greatly. That this decrease is independent of osmotic 
effect is further shown by our work on the effect of ether 
vapor on carbon dioxide production in a frog’s nerve. 
In this work with a frog’s nerve it was found that 
ethyl urethane will reduce carbon dioxide production, 
but that soon after the nerve begins to gain in weight 
the tendency is for this production to increase slightly, 
though not sufficiently to raise it to its normal value. 
Although this point is still under quantitative investi- 
gation, it seems certain that this increase of carbon 
dioxide is casual, and probably due to a sort of water 
rigor. Somewhat similar results are obtained with the 
spider crab’s nerve (Table VIII). Thus we find that 
with a 3 per cent chloral hydrate solution the carbon 
dioxide production is least—about one-third that of the 
normal nerve—while with a 4 per cent solution it is a 
little less than one-half. Investigation of the effect of 
