One of the fundamental characteristics of life is power of adaptation;
it will adapt itself to almost any condition; it is willing and
accommodating. It is like a stream that can be turned into various
channels; the gall insects turn it into channels to suit their ends when
they sting the leaf of a tree or the stalk of a plant, and deposit an
egg in the wound. "Build me a home and a nursery for my young," says the
insect. "With all my heart," says the leaf, and forthwith forgets its
function as a leaf, and proceeds to build up a structure, often of great
delicacy and complexity, to house and cradle its enemy. The current of
life flows on blindly and takes any form imposed upon it. But in the
case of the vegetable galls it takes life to control life. Man cannot
produce these galls by artificial means. But we can take various
mechanical and chemical liberties with embryonic animal life in its
lower sea-forms. Professor Loeb has fertilized the eggs of sea-urchins
by artificial means. The eggs of certain forms may be made to produce
twins by altering the constitution of the sea-water, and the twins can
be made to grow together so as to produce monstrosities by another
chemical change in the sea-water. The eyes of certain fish embryos may
be fused into a single cyclopean eye by adding magnesium chloride to the
water in which they live. Loeb says, "It is _a priori_ obvious that an
unlimited number of pathological variations might be produced by a
variation in the concentration and constitution of the sea water, and
experience confirms this statement." It has been found that when frog's
eggs are turned upside down and compressed between two glass plates for
a number of hours, some of the eggs give rise to twins. Professor Morgan
found that if he destroyed half of a frog's egg after the first
segmentation, the remaining half gave rise to half an embryo, but that
if he put the half-egg upside down, and compressed it between two glass
plates, he got a perfect embryo frog of half the normal size. Such
things show how plastic and adaptive life is. Dr. Carrel's experiments
with living animal tissue immersed in a proper mother-liquid illustrate
how the vital process--cell-multiplication--may be induced to go on and
on, blindly, aimlessly, for an almost indefinite time. The cells
multiply, but they do not organize themselves into a constructive
community and build an organ or any purposeful part. They may be likened
to a lot of blind masons piling up brick and mortar without any
architect to direct their work or furnish them a plan. A living body of
the higher type is not merely an association of cells; it is an
association and coöperation of communities of cells, each community
working to a definite end and building an harmonious whole. The
biochemist who would produce life in the laboratory has before him the
problem of compounding matter charged with this organizing tendency or
power, and doubtless if he ever should evoke this mysterious process
through his chemical reactions, it would possess this power, as this is
what distinguishes the organic from the inorganic.
I do not see mind or intelligence in the inorganic world in the sense in
which I see it in the organic. In the heavens one sees power, vastness,
sublimity, unspeakable, but one sees only the physical laws working on a
grander scale than on the earth. Celestial mechanics do not differ from
terrestrial mechanics, however tremendous and imposing the result of
their activities. But in the humblest living thing--in a spear of grass
by the roadside, in a gnat, in a flea--there lurks a greater mystery. In
an animate body, however small, there abides something of which we get
no trace in the vast reaches of astronomy, a kind of activity that is
incalculable, indeterminate, and super-mechanical, not lawless, but
making its own laws, and escaping from the iron necessity that rules in
the inorganic world.
Our mathematics and our science can break into the circle of the
celestial and the terrestrial forces, and weigh and measure and separate
them, and in a degree understand them; but the forces of life defy our
analysis as well as our synthesis.
Knowing as we do all the elements that make up the body and brain of a
man, all the physiological processes, and all the relations and
interdependence of his various organs, if, in addition, we knew all his
inheritances, his whole ancestry back to the primordial cells from which
he sprang, and if we also knew that of every person with whom he comes
in contact and who influences his life, could we forecast his future,
predict the orbit in which his life would revolve, indicate its
eclipses, its perturbations, and the like, as we do that of an
astronomic body? or could we foresee his affinities and combinations as
we do that of a chemical body? Had we known any of the animal forms in
his line of ascent, could we have foretold man as we know him to-day?
Could we have foretold the future of any form of life from its remote
beginnings? Would our mathematics and our chemistry have been of any
avail in our dealing with such a problem? Biology is not in the same
category with geology and astronomy. In the inorganic world, chemical
affinity builds up and pulls down. It integrates the rocks and, under
changed conditions, it disintegrates them. In the organic world chemical
affinity is equally active, but it plays a subordinate part. It neither
builds up nor pulls down. Vital activities, if we must shun the term
"vital force," do both. Barring accidents, the life of all organisms is
terminated by other organisms. In the order of nature, life destroys
life, and compounds destroy compounds. When the air and soil and water
hold no invisible living germs, organic bodies never decay. It is not
the heat that begets putrefaction, but germs in the air. Sufficient heat
kills the germs, but what disintegrates the germs and reduces them to
dust? Other still smaller organisms? and so on _ad infinitum_? Does the
sequence of life have no end? The destruction of one chemical compound
means the formation of other chemical compounds; chemical affinity
cannot be annulled, but the activity we call vital is easily arrested. A
living body can be killed, but a chemical body can only be changed into
another chemical body.
The least of living things, I repeat, holds a more profound mystery than
all our astronomy and our geology hold. It introduces us to activities
which our mathematics do not help us to deal with. Our science can
describe the processes of a living body, and name all the material
elements that enter into it, but it cannot tell us in what the peculiar
activity consists, or just what it is that differentiates living matter
from non-living. Its analysis reveals no difference. But this difference
consists in something beyond the reach of chemistry and of physics; it
is active intelligence, the power of self-direction, of self-adjustment,
of self-maintenance, of adapting means to an end. It is notorious that
the hand cannot always cover the flea; this atom has will, and knows
the road to safety. Behold what our bodies know over and above what we
know! Professor Czapek reveals to us a chemist at work in the body who
proceeds precisely like the chemist in his laboratory; they might both
have graduated at the same school. Thus the chemist in the laboratory is
accustomed to dissolve the substance which is to be used in an
experiment to react on other substances. The chemical course in living
cells is the same. All substances destined for reactions are first
dissolved. No compound is taken up in living cells before it is
dissolved. Digestion is essentially identical with dissolving or
bringing into a liquid state. On the other hand, when the chemist wishes
to preserve a living substance from chemical change, he transfers it
from a state of solution into a solid state. The chemist in the living
body does the same thing. Substances which are to be stored up, such as
starch, fat, or protein bodies, are deposited in insoluble form, ready
to be dissolved and used whenever wanted for the life processes.
Poisonous substances are eliminated from living bodies by the same
process of precipitation. Oxalic acid is a product of oxidation in
living cells, and has strong poisonous properties. To get rid of it, the
chemist inside the body, by the aid of calcium salts, forms insoluble
compounds of it, and thus casts it out. To separate substances from each
other by filtration, or by shaking with suitable liquids, is one of the
daily tasks of the chemist. Analogous processes occur regularly in
living cells. Again, when the chemist wishes to finish his filtration
quickly, he uses filters which have a large surface. "In living
protoplasms, this condition is very well fulfilled by the foam-like
structure which affords an immense surface in a very small space." In
the laboratory the chemist mixes his substances by stirring. The body
chemist achieves the same result by the streaming of protoplasm. The
cells know what they want, and how to attain it, as clearly as the
chemist does. The intelligence of the living body, or what we must call
such for want of a better term, is shown in scores of ways--by the means
it takes to protect itself against microbes, by the antitoxins that it
forms. Indeed, if we knew all that our bodies know, what mysteries would
be revealed to us!