102 A CHEMICAL SIGN OF LIFE 
The chemical sign of life which we now propose for 
acceptance is in many ways more fundamental than the 
electrical. It is probable, as Waller suggested, that 
the chemical changes underlie and produce the electrical, 
and they produce the functional changes, such as the 
movements which follow the excitation. In the chemical 
changes, then, we seem to be dealing with something 
more fundamental than when dealing with the electrical, 
although, if we admit that all processes of oxidation are 
in reality electrical, this distinction cannot be sustained. 
Wherever Waller has been able to show the electrical 
sign of life, we can show the chemical sign, and we can 
show life at some points where he could not, as in the 
case of the sea algae. These, under our method, respond 
in the same manner as do all other forms of living matter. 
Moreover, we can use this method where it is impos- 
sible to use the electrical; for example, in very minute 
forms of living things, like eggs of small size, bacteria, 
or infusoria. Our method can make it clear that they 
are alive and breathing and responding to changes in 
their environment like every other living thing. It 
appears, then, that this sign of life has also certain 
virtues of its own, although it is not so striking and 
elegant as the method of Waller. It is also not so easy, 
perhaps, for the ordinary man to set up and work 
this apparatus as a galvanometer. But what it lacks 
in ease it makes up in precision, in the quantitative nature 
of its results, and, above all, in its fundamental char- 
acter. By it we get as near as we have yet got to life 
itself. 
In still another way the results which are recorded 
here are of a most fundamental character, for one of the 
