100 A CHEMICAL SIGN OF LIFE 
at every point Waller’s electrical test, is shown to be 
whether or not the tissue respiration can be accelerated 
by an injury. And we can measure this with our new 
apparatus, the biometer, which thus justifies its name, 
although its applicability is far greater than merely 
testing the degree of vitality of a tissue. 
We have now to compare for a moment this criterion 
of life—the chemical—with other criteria which have 
been proposed, and to see whether it lacks anything of the 
precision of these other methods, and whether life can be 
shown to exist by other methods where we cannot prove 
its existence by ours. There is one criterion other than 
the obvious one of growth which has been proposed to 
determine whether a seed or other living thing, or piece 
of a living thing, is alive or not. That is the criterion 
suggested by Waller. It is the electrical sign of life. 
Waller discovered a very remarkable electrical sign of 
life, which may be described as follows: Two electrodes 
are placed on opposite sides of a garden pea which is 
living, the electrodes being connected on the one hand 
with an induction coil and on the other with a sensitive 
galvanometer. A single induction shock is then sent 
through the pea. If the pea is alive, this shock is fol- 
lowed by a remarkable outburst of electromotive force 
in the pea. A current suddenly blazes out, as is shown 
by the deflection of the galvanometer. It is as if the 
pea jumped when stimulated. This current sometimes 
travels in the same direction as the induction shock, 
and sometimes in the opposite direction. Itis of momen- 
tary duration. Waller calls it the blaze current. As 
long as the seed lives, you get it; when the seed dies, you 
do not get it. The dead or anesthetized seed does not 
