"Now, don't worry about it, son," he said hurriedly; "We'll see to it that you aren't punished for it. It's all right. We just want to ask you a few questions." "Sure, Doc; anything," said MacNeil. But he still looked apprehensive. "Have you been dosing yourself pretty regularly with these things?" "Well ... uh ... well, yeah. Sometimes." He smiled feebly. "Sometimes I didn't feel so good, and I didn't want to bother the medics. You know how it is." "Very considerate, I'm sure," said Smathers with just the barest trace of sarcasm, which, fortunately, fell unheeded on MacNeil's ears. "But which ones did you take every day?" "Just the vitamins." He paused. "And ... uh ... maybe an aspirin. The only things I took real regular were the vitamins, though. That's all right ain't it? Ain't vitamins food?" "Sure, son, sure. What did you take yesterday morning, before you got so sick?" "Just the vitamins," MacNeil said stoutly. "I figured that since you docs was takin' care of me, I didn't need no medicine." Dr. Smathers glanced up hopelessly at the other two men. "That eliminates the vitamins," he said, _sotto voce_. He looked back at the patient. "No aspirin? No APC's? You didn't have a headache at all?" MacNeil shook his head firmly. "I don't get headaches much." Again he essayed a feeble smile. "I ain't like you guys, I don't overwork my brains." "I'm sure you don't," said Smathers. Then his eyes gleamed. "You have quite a bit of stomach trouble, eh? Your digestion bad?" "Yeah. You know; I told you about it. I get heartburn and acid stomach pretty often. And constipation." "What do you take for that?" "Oh, different things. Sometimes a soda pill, sometimes milk of magnesia, different things." Smathers looked disappointed, but before he could say anything, Dr. Petrelli's awed but excited voice came from behind him. "Do you take Epsom salts?" "Yeah." "I wonder--" said Petrelli softly. And then he left for the lab at a dead run. * * * * * Colonel Fennister and Major Grodski sat at the table in the lab, munching on banana-pears, blissfully enjoying the sweet flavor and the feeling of fullness they were imparting to their stomachs. "MacNeil can't stay in the service, of course," said Fennister. "That is, not in any space-going outfit. We'll find an Earthside job for him, though. Maybe even give him a medal. You sure these things won't hurt us?" Dr. Pilar started to speak, but Petrelli cut him off. "Positive," said the chemist. "After we worked it out, it was pretty simple. The 'poison' was a chelating agent, that's all. You saw the test run I did for you." The colonel nodded. He'd watched the little chemist add an iron salt to some of the fruit juice and seen it turn red. Then he'd seen it turn pale yellow when a magnesium salt was added. "But what's a chelating agent?" he asked.