By an ingenious device, it is now possible to tell whether a plant,
a leaf, a seed, or a piece of organic tissue is living or dead. A
sure test for the presence of life is very desirable since it at once
informs the experimentalist whether or not the specimen before him can
be made to respond, and live again, or not. It is possible that this
method may be applied to human beings, in the future.
There are two main tests or signs which all living things show and
which are indices of life. One of these is an _electrical_ disturbance.
This was discovered more than a hundred years ago. The other is the
_chemical_ sign, which has only lately been discovered by Professor
Shiro Tashiro, of the University of Chicago.
In a recently published work upon his researches and discoveries in
this field, he says:
“It is a matter of very great interest that I have recently found that
there is always and everywhere an accompanying chemical change of a
particular kind, which is a sure sign of life, and as invariable an
accompaniment of the vital reaction as the electrical change.
“This chemical sign is the sudden outburst of _carbon dioxide_ which
all living things show--plants as well as animals, dry seeds as well
as the nerve tissues of the highest mammals--when they are stimulated
in any way. The instrument which I have made to detect this carbon
dioxide I have called a “Biometer,” because it is an instrument for
the measuring or detecting the amount of life possessed by different
things.”
By means of this instrument, it was shown that _nerves breathe_, that
is to say, they take in oxygen and give off carbon dioxide, just as we
do. Seeds do the same thing, when they are stimulated; every living
thing does so! But the moment that thing is dead, no more carbon
dioxide is given off.
The nervous impulses within the body are closely allied to electricity,
but they are also chemical in nature, to a great extent. Taking in
oxygen and giving off carbon dioxide is essential for their life. The
same sort of thing occurs in the human brain; accompanying all thought
these transformations take place. Some of these are physical in nature,
some vital and some psychical. Professor Tashiro is careful to note
this, for the last sentence in his book is:
“Three kinds of nervous changes, then, occur in our brains, when the
nerve impulses are passing--an electrical change, a chemical change,
and a psychical change. Which is the fundamental change?”
That which makes up our mental life is the psychical change--the
thought itself. For _us_, this is the greatest reality!