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 i 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. 



