24 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 
I 2 3 4 5. 6 7 
cone 
entime- . 
Temper | weient of | stimuta-| tigate pPRAEeE | BRE 
Date R Nerve in tion Taken |° ti Deas atte Te 
D Om Milligrams 2 from Res- pon: cr eo: 
egrees C. piratory Minutes | Minutes 
Chamber 
November 4.. 13 40 (killed) No O.5 Io - 
November 4. . Fe 40 (killed) Yes O.5 10 - 
November s5.. as 16 (normal) No 1.0 Io + 
November 6.. 1s 16 (killed) No 1.0 12 - 
November 7. . 16 16 (normal) No 1.0 10 + 
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 
