"Maybe," Calhoun said, "this isn't so much a new disease as a modification of a very old one. The very ancient Hate Disease—for the most important symptom of this particular malady is the hate it's stirred up. I've seen a number of sick planets—but the hate index on this one earns it a record score." He paused for a moment as the computer did an extra-special burping chuckle, and slipped in 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 controlled in a larger environment. But the check on this molecule isn't working, here!"
The booming voice of the Planetary President went on and on and on. Memoranda of events taking place were handed to him, and he read them and argued with the paras who had tried to rush the north gate of Government Center, to make its inhabitants paras like themselves. But the Planetary President tried to make oratory a weapon against madness.
Calhoun grimaced at the voice. He said fretfully:
"There's a molecule which has to exist because it can. It's a part of a normal environment, but it doesn't normally produce paras. Now it does! Why? What is the compound or the condition that controls its abundance? Why is it missing here? What is lacking? What?"