n an
entire new case of memory cubes. "Hm-m-m ... if what we're looking for
is a vaccine against hate we'd really have something.

"But I'm afraid not. That's too happy an outcome. We'll just call this
Hate Disease, Tallien Three strain. It's standard practice," Calhoun
continued, "to consider that everything that can happen, does.
Specifically, that any compound that can possibly exist, sooner or
later must be formed in nature. We're looking for a particular one. It
must have been formed naturally at some time or another, but never
before has it appeared in quantity enough to threaten a civilization.
Why?"

Murgatroyd licked his right-hand whiskers. He whimpered a little--and
Murgatroyd was a very cheerful small animal, possessed of exuberant
health and a fine zest in simply being alive. Exposed to contagion, it
was the admirable talent of his kind to react instantly and violently,
producing antibodies so promptly that no conceivable disease could
develop. _Tormals_ were cherished and respected members of the
Interstellar Medical Service because they could produce within hours
antibodies for any possible infection, and the synthesis of such
antibodies could be begun and any possible plague defeated. But
Murgatroyd was not happy now.

"It's been known for a long time," said Calhoun impatiently, "that no
form exists alone. Every living creature exists in an environment, in
association with all the other living creatures around it. But this is
true of compounds, too! Anything that is part of an environment is
essential to that environment. So even organic compounds are as much
parts of a planetary life system as ... say ... rabbits on a Terran
type world. If there are no predators, rabbits will multiply until
they starve."

Murgatroyd said, "_Chee!_" as if complaining to himself.

"Rats," said Calhoun somehow angrily, "have been known to do that on a
derelict ship. There was a man named Malthus who said we humans would
some day do the same thing. But we haven't. We've take over a galaxy.
If we ever crowd this, there are more galaxies for us to colonize,
forever! But there have been cases of rats and rabbits multiplying
past endurance. Here we've got an organic molecule that has multiplied
out of all reason! It's normal for it to exist, but in a normal
environment it's held in check by other molecules which in some sense
feed on it; which control the population of this kind of molecule as
rabbits or rats are control