Dr. John Bartok replaced the test tube carefully in its rack with fingers that shook a little. His pleasant, plump-cheeked face had the blank look of a man who has had too great a shock to assimilate, so that for the moment he feels nothing. He got to his feet. Absently he ran stained, spatulate-tipped fingers through his thinning blond hair and groped for a cigarette. The liquid in the test tube caught a pinpoint of light from the fluorescents and thin fumes escaped upwards from its surface. Dr