Anywhen by James Blish

injuring so much as one native. Just how we're going to manage that, I'll have to leave up to you."
    Lea shrugged. He was used to being handed the hard ones.
    "All right. Now what we want to do isn't quite as complicated. We need to capture a number of natives with status among their fellows—warriors will doubtless do; learn more of their language; win their confidence; and explain to them that we have a cure. And we will have to convince them that they must abandon their first natural desire, which will be to give the antivirus to their sick warriors and kings. The stuff won't work with them; they're doomed. Instead, it will have to be given to expectant mothers, exclusively."
    "That's going to take a lot of convincing," Captain Motlow said.
    "Agreed. But that's one of the main reasons why I'm here. Nor is that all. There's a time limit. Unlike human beings, the natives here have a fixed mating season, so all their babies go to term at once, practically speaking. We got here as fast as we could once we learned the story, but we are right on the edge of the whelping season now. If we don't get most of this generation of pregnant females injected—for which native help is imperative; we haven't the manpower to do it ourselves—the race will be wiped out. The male children will die in infancy, and that will be that.
    "That's all I know about the situation, and all anybody knows. So I have to conclude: Gentlemen, you must take it from there."
    A stocky, middle-aged man with completely white hair —Clyde Bixby, the ship's surgeon—raised his hand. "One fact I think you skipped, Doctor," he said. "And I think it's interesting in this context. Why not tell the assembled company what the plague was?"
    "Oh. Sure," Dr. Roche said. "It was tobacco mosaic."
    Nobody but Doc Bixby seemed to believe him at first, and after all, Bixby had already had the benefit of the explanation—or as much of it as Dr. Roche knew. But a lot of them ground out their cigarettes like they were crushing poisonous snakes, all the same. Roche grinned.
    "Don't worry," he said. "One reason tobacco mosaic is so abundant on Earth is because it's harmless to humans. And as far as tobacco growers are concerned, it can be controlled in the fields—not cured, but controlled—by streptomycin spraying."
    "A curious thing in itself," Doc Bixby put in. "Streptomycin is no good at all against any other virus."
    "Well, it's no more than indifferently good against mosaic, either," Dr. Roche emphasized. "But that's not important now. The point is: For the tobacco plant, mosaic is one of the most highly infectious diseases man has ever studied. The virus isn't a tiny but relatively complex organism, as most viruses that attack man and other animals are. Instead, it's a simple chemical compound. You can prepare it in crystal form as easily as you'd make rock salt or rock candy. It isn't alive, not until it gets into the plant cell; the life it leads thereafter is entirely `borrowed' from the host. And it's simple enough chemically so that most reagents—physical or chemical—don't destroy its integrity.
    "The result is that if you walk into a greenhouse where tobacco is growing, and you're smoking a cigarette which was made from the leaf of a plant that had had mosaic, most of the growing plants will come down with the disease. They literally contract it from the smoke. And that seems to be exactly what the Savannahans did. They picked it up from cigarettes the first explorers offered them."
    "As a peace pipe, maybe?" Bixby speculated.
    "Maybe. If so, it's a great fat example of what a mess you can make by pushing an analogy too far."
    "But why were they susceptible in the first place?" I asked.
    Roche spread his hands. "God knows, Hans. It's just lucky for them that we know how the virus operates. It heads right for the chromosomes during cell division, and alters a set of genes in such a way that the daughter cells become susceptible to the disease in its overt, or