Dr. Petrelli raised a thin eyebrow. "What's the difference between a sign and a symptom?" "A sign," said Smathers testily, "is something that can be objectively checked by another person than the patient. Lesions, swellings, inflammations, erratic heartbeat, and so on. A symptom is a subjective feeling of the patient, like aches, pains, nausea, dizziness, or spots before the eyes. "And MacNeil is beginning to get all kinds of symptoms. Trouble is, he's got a record of hypochondria, and I can't tell which of the symptoms are psychosomatic and which, if any, might be caused by the fruit." "The trouble is," said Petrelli, "that we have an unidentifiable disease caused by an unidentifiable agent which is checked by an unidentifiable something in MacNeil. And we have neither the time nor the equipment to find out. This is a job that a fully equipped research lab might take a couple of years to solve." "We can keep trying," said Pilar, "and hope we stumble across it by accident." [Illustration] Petrelli nodded and picked up the beaker he'd been heating over an electric plate. He added a chelating agent which, if there were any nickel present, would sequester the nickel ions and bring them out of solution as a brick-red precipitate. Smathers scowled and bent over his microscope to count more leucocytes. Pilar pushed his notes aside and went over to check his agar plates in the constant-temperature box. The technicians who had been listening to the conversation with ears wide open went back to their various duties. And all of them tried in vain to fight down the hunger pangs that were corroding at their insides. * * * * * Broderick MacNeil lay in his bed and felt pleasantly ill. He treasured each one of his various symptoms; each pain and ache was just right. He hadn't been so comfortable in years. It really felt fine to have all those doctors fussing over him. They got snappy and irritable once in a while, but then, all them brainy people had a tendency to do that. He wondered how the rest of the boys were doing on their diet of banana-pears. Too bad they weren't getting any special treatment. MacNeil had decided just that morning that he'd leave the whole state of his health in the hands of the doctors. No need for a fellow to dose himself when there were three medics on the job, was there? If he needed anything, they'd give it to him, so he'd decided to take no medicine. A delightful, dulling lassitude was creeping over him. * * * * * "MacNeil! _MacNeil!_ Wake up, MacNeil!" The spaceman vaguely heard the voice, and tried to respond, but a sudden dizziness overtook him. His stomach felt as though it were going to come loose from his interior. "I'm sick," he said weakly. Then, with a terrible realization, "I'm really _awful_ sick!"