"You might use that brain of yours," Mary said bitterly. "You're supposed to be a scientist. You have facts. Can't you put them together?" "I don't know." He shrugged, "I've been working on this problem longer than you think. I come down here at night--" "I know. I clean up after you." "I haven't gotten anywhere. Sure, we can isolate the virus. It grows nicely on monkey lung cells. But that doesn't help. The thing has no apparent antigenicity. It parasitizes, but it doesn't trigger any immune reaction. We can kill it, but the strength of the germicide is too great for living tissue to tolerate." "Some people seem to be immune." "Sure they do--but why?" "Don't ask me. I'm not the scientist." "Play like one," Kramer growled. "Here are the facts. The disease attacks people of all races and ages. So far every one who is attacked dies. Adult Europeans and Americans appear to be somewhat more resistant than others on a population basis. Somewhere around sixty per cent of them are still alive, but it's wiped out better than eighty per cent of some groups. Children get it worse. Right now I doubt if one per cent of the children born during the past ten years are still alive." "It's awful!" Mary said. "It's worse than that. It's extinction. Without kids the race will die out." Kramer rubbed his forehead. "Have you any ideas?" "Children have less resistance," Kramer replied. "An adult gets exposed to a number of diseases to which he builds an immunity. Possibly one of these has a cross immunity against Thurston's virus." "Then why don't you work on that line?" Mary asked. "Just what do you think I've been doing? That idea was put out months ago, and everyone has been taking a crack at it. There are twenty-four laboratories working full time on that facet and God knows how many more working part time like we are. I've screened a dozen common diseases, including the six varieties of the common cold virus. All, incidentally, were negative." "Well--are you going to keep on with it?" "I have to." Kramer rubbed his eyes. "It won't let me sleep. I'm sure we're on the right track. Something an adult gets gives him resistance or immunity." He shrugged. "Tell you what. You run those bloods out and I'll go take another look at the data." He reached into his lab coat and produced a pipe. "I'll give it another try." "Sometimes I wish you'd read without puffing on that thing," Mary said. "Your delicate nose will be the death of me yet--" Kramer said. "It's my lungs I'm worried about," Mary said. "They'll probably look like two pieces of well-tanned leather if I associate with you for another year." "Stop complaining. You've gotten me to wear clean lab coats. Be satisfied with a limited victory," Kramer said absently, his eyes staring unseeingly at a row of reagent bottles on the bench. Abruptly he nodded. "Fantastic," he muttered, "but it's worth a check." He left the room, slamming the door behind him in his hurry.