David Wong hurried into the small animal room and paused before a stack of wire cages in which furry creatures darted and squeaked.
"You remember when we were working on Blue Martian, those peculiar mutants we found in our mice, and how I used six of them in trying to make antibodies to the virus?"
"I remember," said Karl. "They were spotted with tufts of white hair on the right forelegs."
David took down a cage, thrust in his hand, and brought out two of the tiny black mice which crawled over his trembling hand. Their right forelegs bore tufts of long white hair.
"These," he said, "are the same mice."
"Their descendants, you mean. Mice don't live that long."
"These mice do. And they'll go on living. For years I've lived in fear that someone would notice and suspect the truth. Just as for years, every time someone has laughed and told me I never seemed to age a day, I've been terrified that he might guess the truth. I'm not aging."
Karl looked dazed. "Well, my boy, you've got a bear by the tail. How did you find the elixir or whatever it is?"
"You remember the early work with radioactive tracers, a couple of hundred years ago, that proved that all our body cells are in a continuous state of flux? There's a dynamic equilibrium between the disintegration and the resynthesis of the essential factors such as proteins, fats and amino groups, but the cell directs all the incoming material into the right chemical structures, under the influence of some organizing power which resides in the cell.