the universe which does not live--the
domain of the chemist and physicist.

Tendency to disturb existing equilibrium,--to take on forms which
succeed one another in definite cycles, is the character of the living
world.

What is the cause of this wonderful difference between the dead particle
and the living particle of matter appearing in other respects identical?
that difference to which we give the name of Life?

I, for one, cannot tell you. It may be that, by and by, philosophers
will discover some higher laws of which the facts of life are particular
cases--very possibly they will find out some bond between
physico-chemical phaenomena on the one hand, and vital phaenomena on the
other. At present, however, we assuredly know of none; and I think we
shall exercise a wise humility in confessing that, for us at least, this
successive assumption of different states--(external conditions
remaining the same)--this _spontaneity of action_--if I may use a term
which implies more than I would be answerable for--which constitutes so
vast and plain a practical distinction between living bodies and those
which do not live, is an ultimate fact; indicating as such, the
existence of a broad line of demarcation between the subject-matter of
Biological and that of all other sciences.

For I would have it understood that this simple Euglena is the type of
_all_ living things, so far as the distinction between these and inert
matter is concerned. That cycle of changes, which is constituted by
perhaps not more than two or three steps in the Euglena, is as clearly
manifested in the multitudinous stages through which the germ of an oak
or of a man passes. Whatever forms the Living Being may take on, whether
simple or complex, _production_, _growth_, _reproduction_, are the
phaenomena which distinguish it from that which does not live.

If this be true, it is clear that the student, in passing from the
physico-chemical to the physiological sciences, enters upon a totally
new order of facts; and it will next be for us to consider how far these
new facts involve _new_ methods, or require a modification of those with
which he is already acquainted. Now a great deal is said about the
peculiarity of the scientific method in general, and of the different
methods which are pursued in the different sciences. The Mathematics
are said to have one special method; Physics another, Biology a third,
and so forth. For my own part, I must confess th