Carbon Dioxide From Nerve Fibres 121 



impulse, the following experiments were performed. If we assume 

 that the condition under which an electrical decomposition takes 

 place is the same -both in the living and the dead nerve, then if the 

 increased C0 2 is due to the current itself, we should expect that when 

 a killed nerve is stimulated by a current, it ought to increase C02 

 production just as much. When I placed two nerves killed by steam 

 in each chamber, and stimulated only one of them, the stimulated 

 nerve did not give any more CO 2 than the unstimulated, using the 

 same strength of current employed in the other experiments. In 

 the next place, it was thought that if the increase of CO 2 is due to 

 direct electrical decomposition, not limited to the point of contact 

 with the electrodes, we ought to get a proportional increase of C0 2 

 by altering the distances through which the current directly passes. 

 The fact was, however, that we could produce an increase of C0 2 

 production by stimulating with electrodes 2 mm. apart as well as by 

 15 mm. apart. Increase of C0 2 , therefore, is due to nervous excita- 

 tion and not to the direct influence of the electric current itself. 



With this consideration, I have proceeded to make a quantitative 

 estimation of CO 2 from the stimulated nerve in the manner described 

 before. The results are shown in Table V. 



Electrical Stimulation of Medullated Nerve. With apparatus 

 2, the output of C0 2 from the excited sciatic nerve of the frog has been 

 quantitatively estimated. As shown below, 10 mgs. of the sciatic 

 nerve gives off 14.2 X icr 7 grams of CO 2 during ten minutes stimula- 

 tion while the resting nerve of the same animal gave off 5.5 X io~ 7 

 grams for the same units. 



Mechanical Stimulation. We have now established the fact that 

 when a nerve is stimulated by an electrical stimulus, it gives off more 

 C0 2 . In order to prove more conclusively that this CO 2 production 

 is due to the passage of a nerve impulse, I have employed several 

 other means which are known to have definite influence on excita- 

 bility of the nerve. So far, the use of these methods has been 

 confined to qualitative experiments, but the results are a sufficient 

 confirmation of the observations made by electrical stimulation. I 

 cite them here as a preliminary report. 



Since the ordinary method for mechanical stimulation cannot be 

 applied directly to the nerve in my apparatus in its present form, I 

 used a different method, namely, crushing the nerve. That, when a 



