40 A CHEMICAL SIGN OF LIFE 



In the next place, it was thought possible that our 

 assumption that the condition under which an electrical 

 decomposition takes place is the same in a living and 

 dead nerve may not be strictly true, but that an electrical 

 current can in soflie way ^rive away carbon dioxide more 

 quickly in the living nerve. Since killing* by steam may 

 also drive out the gas already present in the tissue, the 

 apparent indifference of the dead nerve toward electrical 

 stimulation may not prove that the increased carbon 

 dioxide accompanying stimulation in the living nerve is 

 really a direct result of a change in its vitality, rather 

 than an indirect result of the passage of the electrical cur- 

 rent. If, however, this increased gas production were 

 due to the mere electrical decomposition, which was not 

 limited to the point of contact with the electrode, we 

 ought in the living nerve to get a proportional increase of 

 carbon dioxide by increasing the length of nerve through 

 which the current directly passes. The fact is, however, 

 that we can produce an increase of carbon dioxide by 

 stimulating with electrodes 2 mm. apart, so that only a 

 small portion of the nerve is traversed by the current, 

 as well as by electrodes 15 mm. apart. It makes no 

 difference how much of the nerve is traversed by the 

 current. But it does make a difference how much of 

 the nerve is traversed by the nerve impulse. These 

 experiments suggest very strongly that the increase of 

 carbon dioxide on electrical stimulation is due to the 

 increased metabolic activity during functional activity 

 in the nerve, and is not due to the influence of the 

 electrical current as such. With the aid of other 

 means of stimulation we shall now proceed to prove 

 that all stimulation is accompanied by an increase of 



