CHEMICAL SIGNS OF LIFE 89 
He found that this electrical change—the blaze 
current, as he called it—which appeared when the living 
seed was stimulated by a strong induction current was 
not confined to seeds, but occurred also in other varieties 
of living matter, such as the eyeball, skin, leaves, petals, 
and many other tissues of plants and of animals. This 
momentary electrical change produced thus only by 
living matter is accordingly a reliable sign of life, since 
it does not occur in dead matter. 
When we discovered that even a resting nerve gave 
off carbon dioxide if we used a sensitive method, we 
at once proceeded with some curiosity to determine 
whether or not ordinary seed is chemically inactive. 
We had in mind thus to test Waller’s conclusion that the 
electrical sign in the seed is really the sign of chemical 
changes which, however, were not large enough to be 
detected by ordinary chemical methods. 
Resting metabolism in seeds——If a few kernels of 
wheat are placed in one chamber of the biometer, there 
is no difficulty in showing that seeds give off carbon 
dioxide, since a drop of barium hydroxide in the chamber 
containing the seeds becomes covered after a time with 
a precipitate of barium carbonate. It is true that the 
amount of carbon dioxide given off is exceedingly small, 
being many times less than that of the resting nerve, 
but that this carbon dioxide is produced by a vital 
metabolism is shown by the fact that living seeds 
give far larger amounts of the gas than dead ones. 
A seed respires, therefore, as long as it is alive; and 
we can measure the amount of respiration. Of course 
the mere production of this gas from a seed does not 
mean necessarily that the seed is alive, for the reason 
