"Aw, let 'im alone," Max muttered. "Pat hasn't done anything." He went waveringly to the microscope, took a tiny sliver from his finger, suspended it in a slide and slipped it under the lens with detached habitual dexterity. "Something funny going on," he said to June. "Symptoms don't feel right." After a moment he straightened and motioned for her to look. "Leucocytes, phagocytes--" He was bewildered. "My own--" She looked in, and then looked back at Pat in a growing wave of horror. "They're not your own, Max!" she whispered. Max rested a hand on the table to brace himself, put his eye to the microscope, and looked again. June knew what he saw. Phagocytes, leucocytes, attacking and devouring his tissues in a growing incredible horde, multiplying insanely. _Not his phagocytes! Pat Mead's!_ The Meads' evolved cells had learned too much. They were contagious. And not Pat Mead's.... How much alike _were_ the Meads?... Mead cells contagious from one to another, not a disease attacking or being fought, but acting as normal leucocytes in whatever body they were in! The leucocytes of tall, red-headed people, finding no strangeness in the bloodstream of any of the tall, red-headed people. No strangeness.... A toti-potent leucocyte finding its way into cellular wombs. The womblike life tanks. For the men of the _Explorer_, a week's cure with deep melting to de-differentiate the leucocytes and turn them back to normal tissue, then regrowth and reforming from the cells that were there. From the cells that _were_ there. _From the cells that were there...._ "Pat--" "I know." Pat began to laugh, his face twisted with sudden understanding. "I understand. I get it. I'm a contagious personality. That's funny, isn't it?" Max rose suddenly from the microscope and lurched toward him, fists clenched. Pat caught him as he fell, and the bewildered stretcher bearers carried him out to the tanks. * * * * * For a week June tended the tanks. The other women volunteered to help, but she refused. She said nothing, hoping her guess would not be true. "Is everything all right?" Elsie asked her anxiously. "How is Jerry coming along?" Elsie looked haggard and worn, like all the women, from doing the work that the men had always done. "He's fine," June said tonelessly, shutting tight the door of the tank room. "They're all fine." "That's good," Elsie said, but she looked more frightened than before. June firmly locked the tank room door and the girl went away.