Pat's recovery was rapid and uneventful. The following morning she got up and had coffee with us. In a couple of days she was getting around well although the Chief wisely insisted she rest for long periods and absolutely refused to let her work in the Lab. Part of her restless energy she expended on preparing tasty meals for us until we both began to grumble about our expanding waistlines. There was no sign that the new disease had ill effects other than what she had already suffered. Whether or not she was sterile was a question that would have to wait. I had no intention of putting it to the test for a good long time. To work for the cause of science was all very well but I could see no point in sacrificing my love to it. The new virus was christened FS for female sterility and we re-named the old one MS for male sterility. The new one was easy to grow. It thrived on fertilized eggs, in ferrets, hamsters, mice and monkeys; in every animal we could find. With passage through numerous generations it became more virulent until, in its final form, it caused abortion in all pregnant animals. Invariably, after recovery of the animals, our pathologists were unable to find any developing eggs in their ovaries. Because of their short breeding cycle we worked mainly with hamsters, those fat little relatives of the guinea pig. Even the amazing fertility of the hamster was stopped by the FS virus. "It looks as if we have the answer for the Russians," I said exultantly after we had tallied our results some weeks later. "I'm not so sure, John, not so sure at all," Hallam said thoughtfully. "Why is that, Sir?" "Have you ever thought of the consequences of sterilizing every mammal on earth, and perhaps the birds and other animals too?" he asked. "This FS virus is powerful. If we start another pandemic it could get away from us. It might increase in power still more, though God knows it's bad enough. And obviously we can't inoculate every animal of all the species it may affect even when we find the vaccine to counteract it. We'd have to build another Noah's Ark and take it out in the middle of the ocean to be sure we could save them from extinction." "We have a Noah's Ark now," I suggested. "We could isolate the Americans from Asia, Europe and Africa. Australia and New Zealand could do the same. We are doing it for the measlepox right now until there is enough vaccine to go around." "That's true, although it wouldn't be difficult for the Russians to smuggle the virus ashore. They might do it if they thought they were licked. The dying soldier often tries to drag his enemy down with him."