"No biological generalization rests on a wider series of observations,
or has been subjected to a more critical scrutiny, than that every
living organism has come into existence from a living portion or
portions of a pre-existing organism."[3]
"Was there anything so absurd as to believe that a number of atoms, by
falling together of their own accord, could make a sprig of moss, a
microbe, a living animal? ... It is utterly absurd.... Here scientific
thought is compelled to accept the idea of creative power. Forty years
ago I asked Liebig ... if he believed that the grass and flowers, which
we saw around us, grew by mere mechanical force. He answered, 'No more
than I could believe that a book of botany describing them could grow by
mere chemical force.'"[4]
"Let them not imagine that any hocus-pocus of electricity or viscous
fluids would make a living cell.... Nothing approaching to a cell of
living creature has ever yet been made.... No artificial process
whatever could make living matter out of dead."[5]
[Footnote 3: P.C. Mitchell, in Encyclopædia Britannica, Vol. III, p.
952.]
[Footnote 4: Lord Kelvin in the London _Times_, May 4, 1903.]
[Footnote 5: Lord Kelvin, to a class of Medical Students, October 28,
1904.]
I
Ever since René Descartes, in his Holland laboratory, dissected the
heads of great numbers of animals in order to discover the processes of
imagination and memory, men have been seeking a physical or
materialistic answer to such questions as, What is life? What is it to
be alive? How shall we distinguish the living from the not-living?
No one of to-day, in the light of the correlation of vital processes
with the general law of the conservation of energy, believes that life
in plants and animals is a separate entity which may exist outside of
and apart from matter. In a scientific sense, we only know life by its
association with living matter, which in its simplest form is known as
_protoplasm_. The latter has been termed the physical basis of life, and
so far as we know every material living thing is composed wholly of
protoplasm and of the structures which it has built up.
This grayish, viscid, slimy, semi-transparent, semi-fluid substance,
similar to the white of an egg, is the most puzzling, the most wonderful
material with which science has to deal. Chemically it is composed of
various proteids, fats, carbohydrates, etc., and these in turn of but
very few elements, all of which are common, and none of which are
peculiar to protoplasm itself. And yet its essential properties, its
mechanical as well as its chemical make-up, have baffled the resources
of our wisest men with all their retorts and microscopes and other
instruments of precision.
Protoplasm is essentially uniform and similar in appearance and
properties wherever found, whether in the tissues of the human body, in
a blade of grass, or in the green slime of a stagnant pool. And yet
probably no two samples of protoplasm are ever exactly similar in all
respects, though we may never be able to detect their precise
differences. These differences are due to the fact that the stuff is
_alive_, and within it are constantly going on those changes
accompanying metabolism, or the building up and tearing down processes
that always accompany life. All separate masses of protoplasm, such as
the one-celled amoeba or the individual cells of our own bodies, are
constantly taking in food and as constantly throwing off wastes. Hence,
in the very nature of things, it is impossible to find any mass of
protoplasm absolutely pure. And a further and impassable barrier to
chemical analysis, or indeed to any adequate scientific examination,
lies in the fact that we can never deal with protoplasm exactly as it
is, since no analysis can be performed upon it without destroying its
life. And yet even dead protoplasm, and especially its most
characteristic constituent, _proteid_, has been found the most difficult
material in the world to analyze, and nobody as yet pretends to know its
exact chemical make-up.
The constant effort of natural science to press back the boundaries of
the unknown is very liable to obscure some of the things most essential
to any system of clear thinking regarding these matters. We are so prone
to think that if only our microscopes were a little stronger, if only we
could devise more effective methods of staining or of chemical analysis
or chemical synthesis, we might really find out what life is, or what
matter itself is; in short, that we might be able to solve in a
scientific way the old, old riddle of existence. But already we have
about reached the limits of the powers of the microscope; and even if we
could devise a way of seeing the ultimate structures of which protoplasm
is composed, how would we be any better off? Would we not have to
attribute to each constituent of this living substance the properties
which we now attribute to the whole?--that is, the properties which we
attribute to masses of protoplasmic units, such as plants, or birds, or
human beings?
We look at ourselves and we feel sure that we have a separate and real
existence, that we are rationally conscious and are endowed with choice
and free will. We can say almost as much for an intelligent bird or dog.
But we hesitate to say how many of these powers or characteristics of
free and independent personality can be assigned to the unicellular
organisms, such as the amoeba or the corpuscles of our blood. These
one-celled creatures are also alive, are just as truly alive as are
those composed of many cells. Even the corpuscles of which our bodies
are composed move, and eat, and grow, and seem really endowed with
intelligence like the higher forms of life. Suppose we could go further
than is now possible and could lay bare the ultimate make-up of the
_chromatin_ of these one-celled creatures, would we even then be able to
prove that life with all its properties is inherent in these material
components of the cells? In other words, would we really solve anything
after all? Or would we not rather be compelled to acknowledge that the
simplest, the most truly rational view of the question is that in living
matter we have merely a special manifestation of the presence and the
direct action of the God of nature which we cannot so readily recognize
in not-living matter? This, it seems to me, is all that we really know,
and all that we are likely ever to know.
When we examine carefully the differences between the living and the
not-living, we see that the chief difference between them is in _their
origin_. The matter of growth is not a real distinction; for crystals
grow on the outside, while inorganic liquids grow by intussusception, as
when a soluble substance is added to them, in very much the same way as
an animal grows by the ingestion of food. Even movement is hardly an
absolute distinction between the living and the not-living; for no
movement can be detected in quiescent seeds, which may lie dormant for
thousands of years; and on the other hand inorganic foams when brought
into contact with liquids of different composition display movements
that very closely simulate those of the living matter. Lastly,
irritability, though so notably characteristic of living matter, is
scarcely peculiar to it, for many inorganic substances seem almost as
definitely responsive to external stimulation. But in the matter of
_their origin_ there is a real and a most fundamental difference. All
living substance arises only from other substance already living. It
cannot arise from the not-living; or at least it never has done so since
the beginning of scientific observation, though on this point have been
concentrated the learning and the laboratory technique of thousands of
chemists and microscopists.
It may not be out of place to quote here from one of the classics
dealing with this subject,--words that are just as true to-day as when
first written nearly half a century ago:
"Let us place vividly in our imagination the picture of the two great
kingdoms of nature,--the inorganic and the organic,--as these now stand
in the light of the Law of Biogenesis. What essentially is involved in
saying that there is no spontaneous generation of life? It is meant that
the passage from the mineral world to the plant or animal world is
hermetically sealed on the mineral side. This inorganic world is staked
off from the living world by barriers that have never yet been crossed
from within. No change of substance, no modification of environment, no
chemistry, no electricity, nor any form of energy, nor any evolution,
can endow a single atom of the mineral world with the attribute of
life. Only by the bending down into this dead world of some living form
can these dead atoms be gifted with the properties of vitality; without
this preliminary contact with life they remain fixed in the inorganic
sphere forever.
"It is a very mysterious law which guards in this way the portals of the
living world. And if there is one thing in nature more worth pondering
for its strangeness, it is the spectacle of this vast helpless world of
the dead cut off from the living by the Law of Biogenesis, and denied
forever the possibility of resurrection within itself. The physical laws
may explain the inorganic world; the biological laws may account for the
development of the organic. But of the point where they meet,--of that
strange border-land between the dead and the living,--science is silent.
It is as if God had placed everything in earth and heaven in the hands
of nature, but had reserved a point at the genesis of life for His
direct appearing."[6]
[Footnote 6: Henry Drummond, "Natural Law in the Spiritual World,"
Chapter I.]
It would be superfluous to emphasize further this great outstanding fact
that the not-living cannot become the living by any of the processes
which we call natural; and it would be presumptuous to attempt to
emulate these eloquent words by seeking to emphasize the completeness
with which this great Law of Biogenesis confirms the truth of a real
Creation; for the supreme grandeur and importance of this law could be
only obscured by so doing.