Responsive movements being a test of life, we shall try to construct a
scale with which the height of livingness may be measured. What is the
difference between the living and the dead? The living answers to a
shock from without; the most lively gives the most energetic, the torpid
or dying the feeblest, and the dead no answer at all. Thus life may be
tested by shocks from without, the size of the answer being the gauge of
vitality. The answer of the strong will be violent and almost explosive
in its intensity, while the weakling will barely protest. The responsive
movements may be recorded by suitable apparatus. The successive
responses to similar shocks will remain uniform, if the living tissue
remained always the same. But the living organism is always in a state
of change for environment is always building us anew, and we are
changing everyday of our life. We are thus subject to change, some day
we are in a state of high exuberance, and other time in a state of
lowest depression: we pass through numerous phases between the two
extremes. Not merely does the present modify, but there is also the
subtle impress of memory of the past. The sum total of all these
characterise one individual from another. How is the hidden to be made
manifest? To test the genuineness of a coin, we strike it and the sound
response betrays the true from the false. The genuine rings true and the
other gives a false note. In this way perhaps the inner history of
different lives may be revealed by shocks and the resulting response.