Calhoun opened a compartment of the kit, whose miniscule test tubes and pipettes gleamed in the torchlight. He absorbedly transferred the reddish fluid to a miniature filter-barrel, piercing a self-healing plastic cover to do so. He said, "You're a pre-med of course. The way you talk—"
"I was an intern," said Kim. "Now I'm pre-corpse."
"I doubt that last," said Calhoun. "But I wish I had some distilled water . . . this is anticoagulant." He added a trace of a drop to the sealed, ruddy fluid. He shook the whole filter to agitate it. The instrument was hardly bigger than his thumb. "Now a clumper . . ." He added a minute quantity of a second substance from an almost microscopic ampule. He shook the filter again. "You can guess what I'm doing. With a decent lab I'd get the structure and formula of the antibody Murgatroyd has so obligingly turned out for us. We'd set to work synthesizing it, and in twenty hours we would have it coming out of the reaction flasks in quantity. But there is no lab."
"There's one in the city," said the gaunt young man hopelessly. "It was for the colonists who were to come. And we were staffed to give them proper medical care. When the plague came, our doctors did everything imaginable. They not only tried the usual culture tricks, but they cultured samples of every separate tissue in fatal cases. They never found a single organism, even with electron microscopes, that would produce the plague." He said with a sort of weary pride, "Those who'd been exposed worked until they had the plague, and then others took over. Every man worked as long as he could make his brain serve him."
Calhoun squinted through the glass tube of the filter at the light of the sputtering torch.
"Almost clumped," he said. Then he added, "I suspect there's been some very fine laboratory work done somewhere to give the invaders their confidence of immunity to this plague. They landed and instantly set to work to mop up the city—to complete the job the plague hadn't quite finished. I suspect there could have been some fine lab work done to make plague mechanism undetectable. I don't like the things I'm forced to suspect!"
He inspected the glass filter again.
"Somebody," he said coldly, "considered that my arrival would be an unfavorable circumstance to him and what he wanted to happen. I think it is. He tried to kill me. He didn't. I'm afraid I consider his existence an unfavorable circumstance." He paused, and said very measuredly, "Cooperating with a plague is a highly technical business; it needs as much information as fighting a plague. Cooperation could no more be done from a distance than fighting it. If the invaders had come to fight the plague, they'd have sent their best medical men to help. If they came to assist it, they'd have sent butchers, but they'd also send the very best man they had to make sure that nothing went wrong with the plague itself. The logical man to be field director of the extermination project would be the man who'd worked out the plague himself." He paused again, and said icily, "I'm no judge to pass on anybody's guilt or innocence or fate, but as a Med Service man I've authority to take measures against health hazards!"
He began to press the plunger of the filter, judging by the wavering light of the torch. The piston was itself the filter, and on one side a clear, mobile liquid began very slowly to appear.
"Just to be sure, though—you said there was a lab in the city and the doctors found nothing."
"Nothing," agreed Kim hopelessly. "There'd been a complete bacteriological survey of the planet. Nothing new appeared. Everybody's oral and intestinal flora were normal. Naturally, no alien bug would be able to compete with the strains we humans have been living with for thousands of years. So there wasn't anything unknown in any culture from any patient."
"There could have been a mutation," said Calhoun. He watched the clear serum increase. "But if your doctors couldn't pass the disease—"
"They could!" said Kim bitterly. "A massive shot of assorted bugs would pass it, breathed or swallowed or smeared on the skin. Experimental animals could be given the plague. But no one organism could be traced as giving it. No pure culture would!"
Calhoun continued to watch the clear fluid develop on the delivery side of the filter piston. Presently there was better than twelve cubic centimeters of clear serum on one side, and an almost solid block of clumped blood cells on the other. He drew off the transparent fluid with a fine precision.
"We're working under far from aseptic conditions," he said wryly, "but we have to take the chances. Anyhow, I'm getting a hunch. A pathogenic mechanism that isn't a single, identifiable bug—it's not natural. It smells of the laboratory, just as uniformed murderers who are immune to a plague do. It's not too wild a guess to suspect that somebody worked out the plague as well as the immunization of the invaders. That it was especially designed to baffle the doctors who might try to fight it."
"It did," agreed Kim bitterly.
"So," said Calhoun, "maybe a pure culture wouldn't carry the plague. Maybe the disaster-producing apparatus simply isn't there when you make pure cultures. There's even a reason to suspect something specific. Murgatroyd was a very sick animal. I've only known of one previous case in which a tormal reacted as violently as Murgatroyd did to an injection. That case had us sweating."
"If I were going to live," said Kim grimly, "I might ask what it was."
"Since you're going to," Calhoun told him, "I'll tell you. It was a pair of organisms. Separately, they were so near harmless as makes no difference. Together, their toxins combined to be pure poison. It was synergy. They were a synergic pair which, together, were like high explosive. That one was the devil to track down!"
He went back across the glade. Murgatroyd came skipping after him, scratching at the anesthetic patch on his side.
"You go first," said Calhoun briefly to Helen Jons. "This is an antibody serum. You may itch afterward, but I doubt it. Your arm, please."
She bared her pitifully thin arm. He gave her practically a cc of fluid which—plus corpuscles and some forty-odd other essential substances—had been circulating in Murgatroyd's bloodstream not long since. The blood corpuscles had been clumped and removed by one compound plus the filter, and the anticoagulant had neatly modified most of the others. In a matter of minutes, the lab kit had prepared as usable a serum as any animal-using technique would produce. Logically, the antibodies it contained should be isolated and their chemical structure determined. They should be synthesized, and the synthetic antibody-complex administered to plague victims. But Calhoun faced a group of people doomed to die. He could only use his field kit to product a small-scale miracle for them. He could not do a mass-production job.
"Next!" said Calhoun. "Tell them what it's all about, Kim."
The gaunt young man bared his own arm. "If what he says is so, this will cure us. If it isn't so, nothing can do us any more harm."
And Calhoun briskly gave them, one after another, the shots of what ought to be a curative serum for an unidentified disease which he suspected was not caused by any single germ, but by a partnership. Synergy is an acting together. Charcoal will burn quietly. Liquid air will not burn at all. But the two together constitute a violent explosive. The ancient simple drug sulfa is not intoxicating. A glass of wine is not intoxicating. But the two together have the kick of dynamite. Synergy in medicine is a process by which, when one substance with one effect is given in combination with another substance with another effect, the two together have the consequences of a third substance intensified to fourth or fifth or tenth power.
"I think," said Calhoun when he'd finished, "that by morning you'll feel better—perhaps cured of the plague entirely and only weak from failure to force yourselves to take nourishment. If it turns out that way, then I advise you all to get as far away from the city as possible for a considerable while. I think this planet is going to be repopulated. I suspect that shiploads of colonists are on the way here now, but not from Dettra, which built the city. And I definitely guess that, sick or well, you're going to be in trouble if or when you contact the new colonists."