Eventually Calhoun came to the solution of coffee. He mixed it with his experimental microscope-animal zoo, and the paramecia died. Rotifers ceased to whirl and dart about upon their sub-miniature affairs. When an infusion of coffee from the food shop was added to the liquid environment of one-celled animals, they died.
Calhoun checked. It was so. He made an infusion of coffee from the Med Ship's stores. It was not so. Coffee from the ship was not fatal to paramecia. Coffee from the shop was. But it would not follow that coffee from the shop would be fatal to humans. The alcoholic content of beer is fatal to paramecia. Wine is a fair antiseptic. No! The food store coffee could very well be far less toxic than the wildest of mouthwashes, and still kill the contents of Calhoun's ditch-water zoo.
However, the point was that something existed which allowed infections to thrive unhindered in human bodies. Something destroyed the body's defenses against infections. Nothing more would be needed to make the appearance of a plague. Every human being carries with him the seeds of infection, from oral bacteria to intestinal flora, and even often streptococci in the hair follicles of the skin. Destroy the body's means of defense and anyone was bound to develop one of the diseases whose sample bacteria he carries about with him.
Instantly one ceased to think of the plague on Kryder II—and Castor IV before it—instantly one ceased to think of the epidemic as an infection miraculously spreading without any germ or bacterium or virus to carry it, instantly one thought of it as a toxin only, a poison only, a compound as monstrously fatal as the toxin of—say—the bacillus clostridium botulinum. Immediately everything fell into place. The toxin that could simulate a plague could be distributed on a foodstuff: grain or meat or neatly packaged coffee. It would be distributed in such dilution that it was harmless. It would not be detected by any culture-medium process. In such concentration as humans would receive, it would have one effect, and one effect only. It would hinder the body's formation of antibodies. It would prevent the production of those compounds which destroy infective agents to which human beings are exposed. It would simply make certain that no infection would be fought. Antibodies introduced from outside could cure a disease the body could not resist, but there would always be other diseases. . . . Yet, in a concentration greater than body fluids could contain, it killed the creatures that thrived in ditch water.
Calhoun consulted the slip of paper the computer had printed out for him. He went down to the ship's stores. A Med Ship carries an odd assortment of supplies. Here were the basic compounds from which an unlimited number of other compounds could be synthesized. With the computer-slip for a prescription form, he picked out certain ones. He went back to the ditch-water samples presently. He worked very painstakingly. Presently, he had a whitish powder. He made a dilute—a very dilute solution of it. He added that solution to ditch water. The paramecia and rotifers and other tiny creatures swam about in bland indifference. He put in a trace of coffee decoction. Presently, he was trying to find out how small a quantity of his new solution, added to the coffee infusion, made it harmless to paramecia.
It was not an antidote to the substance the coffee contained. It did not counter the effects of that monstrously toxic substance, but it combined with that substance. It destroyed it; it was the answer to the plague on Kryder II.
It was broad daylight when he'd finished the horribly tedious detail work the problem had required. In fact, it was close to sundown. He said tiredly to Murgatroyd, "Well, we've got it!"
Murgatroyd did not answer. Calhoun did not notice for a moment or so. Then he jerked his head about.
Murgatroyd lay on the Med Ship floor, his eyes half-closed. His breath came in quick, shallow pantings.
He'd eaten coffeebeans when they fell on the floor of the control-room. Calhoun picked him up, his lips angrily compressed. Murgatroyd neither resisted nor noticed. Calhoun examined him with a raging, painstaking care.
Murgatroyd was ill. He came of a tribe which was never sick of any infectious disease; they reacted with explosive promptness to any trace of contagion and produced antibodies which would destroy any invading pathogen. His digestive system was normally no less efficient, rejecting any substance which was unwholesome. But the toxic compound which caused the plague on Kryder II was not unwholesome in any direct sense. It did not kill anybody, by itself. It simply inhibited, it prevented, the formation of those antibodies which are a creature's defense against disease.
Murgatroyd had a fully developed case of pneumonia. It had developed faster in him than in a human being. It was horribly more severe. He'd developed it from some single diplococcus pneumonia upon his fur, or perhaps on Calhoun's garments, or possibly from the floor or wall of the Med Ship. Such microorganisms are everywhere. Humans and animals are normally immune to any but massive infection. But Murgatroyd was at the very point of death from a disease his tribe normally could not—could not!—contract.
Calhoun made the tests required to make him absolutely certain. Then he took his new solution and prepared to make use of it.
"Fortunately, Murgatroyd," he said grimly, "we've something to try for this situation. Hold still!"
VI
Murgatroyd sipped a cup of coffee with infinite relish. He finished it. He licked the last drop. He offered it to Calhoun and said inquiringly, "Chee?"
"It probably won't hurt you to have one more cup," said Calhoun. He added irrelevantly, "I'm very glad you're well, Murgatroyd!"
Murgatroyd said complacently, "Chee-chee!"
Then the space communicator said metallically, "Calling Med Ship! Calling Med Ship! Calling Med Ship Aesclipus Twenty! Ground calling Aesclipus Twenty!"
The Med Ship was then in orbit around Kryder II. It was a sound, high orbit, comfortably beyond atmosphere. Calhoun was officially waiting for word of how his communication and instruction to the authorities aground had turned out. He said, "Well?"
"I'm the Planetary Health Minister," said a voice. Somehow it sounded infinitely relieved. "I've just had reports from six of our hospitals. They check with what you told us. The paramecia test works. There were a number of different foods—ah—contaminated at their packaging points, so that even if someone had identified one food as the cause of the plague in one place, in another area it wouldn't be true. It was clever! It was damnably clever! And of course we've synthesized your reagent and tried it on laboratory animals we were able—by your instructions—to give the plague."
"I hope," said Calhoun politely, "that the results were satisfactory."
The other man's voice broke suddenly.
"One of my children . . . he will probably recover, now. He's weak. He's terribly weak! But he'll almost certainly live, now that we can protect him from reinfection. We've started planet-wide use of your reagent."
"Correction," said Calhoun. "It's not my reagent. It is a perfectly well-known chemical compound. It's not often used, and perhaps this is its first use medically, but it's been known for half a century. You'll find it mentioned . . ."
The voice at the other end of the communication link said fiercely, "You will excuse me if I say nonsense! I wanted to report that everything you've told us has proved true. We have very many desperately ill, but new patients have already responded to medication to counter the—contamination of food they'd taken. They've gotten thoroughly well of normal disease and haven't developed others. Our doctors are elated. They are convinced. You can't have any idea how relieved . . ."