these analogies will in any way serve as explanations. We should rather seek to derive the vital from the physical phenomenon. This is the sole ambition of the physiologist. To derive the physical from the vital phenomenon would be unreasonable. We do not attempt to do this here. It is nevertheless true that analogies are of service, were it only to shake the support which, from the time of Aristotle, has been accorded to the division of the bodies of nature into psuchia and apsuchia—i.e., into living and brute bodies.
§ 2. The Brownian Movement.
The Existence of the Brownian Movement.—The
simplest way of judging of the working activity of
matter is to observe it when the liberty of the
particles is not interfered with by the action of the
neighbouring particles. We approximate to this
condition when we watch, through the microscope,
grains of dust suspended in a liquid, or globules of
oil suspended in water. Now what we see is well
known to all microscopists. If the granulations are
sufficiently small, they seem to be never at rest.
They are animated by a kind of incessant tremor;
we see the phenomena called the "Brownian movement."
This movement has struck all observers since
the invention of the magnifying glass or simple
microscope. But the English botanist, Brown, in
1827, made it the object of special research and gave
it his name. The exact explanation of it remained
for a long time obscure. It was given in 1894 by
M. Gouy, the learned physicist of the Faculty of
Lyons.
