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 50 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 



