A CHEMICAL SIGN OF LIFE 



as we have examined, it has been found by Waller that 

 the vitality persists even as long as nineteen hours 

 after removal from the body. These facts are proof, 

 therefore, that the observations made on the carbon 

 dioxide production of isolated nerves are really made on 

 active living nerves, and they may be regarded as quali- 

 tatively similar to what would happen in the normal 

 nerve in situ were we able to measure its carbon dioxide 

 production. 



TABLE I 



COMPARISON BETWEEN NORMAL AND KILLED (BY STEAM) NERVES OF SPIDER CRAB 



If the carbon dioxide is produced by vital activity, 

 its production should be diminished when the nerve is 

 killed. This we can demonstrate by placing a nerve 

 killed by steam in one chamber of the biometer and an 

 equal weight of a normal living nerve in the other 

 chamber and then comparing simultaneously the output 

 of carbon dioxide in the living and dead nerves. It is 

 found that the living nerve continues to give off carbon 

 dioxide, while the dead gives off extremely little, the 

 difference between the two becoming more marked as 

 time goes on. Such a comparison between two nerves 

 of the spider crab is given in Table I, from which it 



