oluble 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!

IV

Life goes up-stream--goes against the tendency to a static equilibrium
in matter; decay and death go down. What is it in the body that
struggles against poisons and seeks to neutralize their effects? What is
it that protects the body against a second attack of certain diseases,
making it immune? Chemical changes, undoubtedly, but what brings about
the chemical changes? The body is a _colony_ of living units called
cells, that behaves much like a colony of insects when it takes measures
to protect itself against its enemies. The body forms anti-toxins when
it has to. It knows how to do it as well as bees know how to ventilate
the hive, or how to seal up or entomb the grub of an invading moth.
Indeed, how much the act of the body, in encysting a bullet in its
tissues, is like the act of the bees in encasing with wax a worm in the
combs!

What is that in the body which at great altitudes increases the number
of red corpuscles in the blood, those oxygen-bearers, so as to make up
for the lessened amount of oxygen breathed by reason of the rarity of
the air? Under such conditions, t