CHEMICAL SIGNS OF IRRITABILITY 39 



6.yXio~ 7 g. 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 i4.2Xio~ 7 g. of the gas during ten minutes of 

 stimulation as compared with 5.5Xio~ 7 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 carbon dioxide 

 than the unstimulated when the same strength of current 

 is employed as was used in the other experiments. 



