"Incredible," Hamelin murmured. "That enormous object can process only one man at a time?" "That's right," Mudgett said. "Luckily it doesn't have to treat all the body cells directly. It works through the blood, re-selfing the cells by means of small changes in the serum chemistry." "What kind of changes?" "Well," Carson said, choosing each word carefully, "that's more or less a graveyard secret, Mr. Secretary. We can tell you this much: the machine uses a vast array of crystalline, complex sugars which _behave_ rather like the blood group-and-type proteins. They're fed into the serum in minute amounts, under feedback control of second-by-second analysis of the blood. The computations involved in deciding upon the amount and the precise nature of each introduced chemical are highly complex. Hence the size of the machine. It is, in its major effect, an artificial kidney." "I've seen artificial kidneys in the hospitals," Hamelin said, frowning. "They're rather compact affairs." "Because all they do is remove waste products from the patient's blood, and restore the fluid and electrolyte balance. Those are very minor renal functions in the higher mammals. The organ's main duty is chemical control of immunity. If Burnet and Fenner had known that back in 1949, when the selfing theory was being formulated, we'd have had Re-Education long before now." "Most of the machine's size is due to the computation section," Mudgett emphasized. "In the body, the brain-stem does those computations, as part of maintaining homeostasis. But we can't reach the brain-stem from outside; it's not under conscious control. Once the body is re-selfed, it will re-train the thalamus where we can't." Suddenly, two swinging doors at the base of the machine were pushed apart and a mobile operating table came through, guided by two attendants. There was a form on it, covered to the chin with a sheet. The face above the sheet was immobile and almost as white. Hamelin watched the table go out of the huge cavern with visibly mixed emotions. He said: "This process--it's painful?" "No, not exactly," Carson said. The motive behind the question interested him hugely, but he didn't dare show it. "But any fooling around with the immunity mechanisms can give rise to symptoms--fever, general malaise, and so on. We try to protect our subjects by giving them a light shock anesthesia first." "Shock?" Hamelin repeated. "You mean electroshock? I don't see how--" "Call it stress anesthesia instead. We give the man a steroid drug that counterfeits the anesthesia the body itself produces in moments of great stress--on the battlefield, say, or just after a serious injury. It's fast, and free of after-effects. There's no secret about that, by the way; the drug involved is 21-hydroxypregnane-3,20 dione sodium succinate, and it dates all the way back to 1955." "Oh," the under-secretary said. The ringing sound of the chemical name had had, as Carson had hoped, a ritually soothing effect.