Beside him was the great panel of the mnemonic eraser with its thousand unblinking eyes. The helmetlike prober cabled to this calculator was fastened about his skull, and he could no longer see the professor who was lecturing in the amphitheater above. But along his body he could see the group of medical students. They were looking at him with great interest, too young not to let the human drama interfere with their technical education.
The professor, however, droned in a purely objective voice. "The mnemonic eraser can selectively shunt from the brain any identifiable category of memory, and erase the synaptic patterns associated with its translation into action. Circulating memory is disregarded. The machine only locates and shunts out those energies present as permanent memory. These are there in part as permanently echoing frequencies in closed cytoplasmic systems. These systems are in contact with the rest of the nervous system only during the phenomenon of remembrance. Remembrance occurs when, at all the synapses in a given network 'y,' the permanently echoing frequencies are duplicated as transient circulating frequencies.
"The objective in a total operation of the sort before us is to distinguish all the stored permanent frequencies, typical of the personality you wish to extinguish, from the frequencies typical of the other personality present in the brain."
Major Grey's face, very tired, but still wearing a mask of adamant reassurance, came into Bill's vision. "There will be a few moments of drug-induced terror, Bill. That is necessary for the operation. I hope knowing it beforehand will help you ride with it. It will not be for long." He squeezed Bill's shoulder and was gone.
"The trick was learned early in our history, when this type of total operation was more often necessary," the professor continued. "It is really quite simple to extinguish one personality while leaving the other undisturbed. The other personality in the case before us has been drug-immobilized to keep this one from shifting. At the last moment, this personality before us will be drug-stimulated to bring it to the highest possible pitch of total activity. This produces utterly disorganized activity, every involved neuron and synapse being activated simultaneously by the drug. It is then a simple matter for the mnemonic eraser to locate all permanently echoing frequencies involved in this personality and suck them into its receiver."
Bill was suddenly aware that a needle had been thrust into his arm. Then it was as though all the terror, panic and traumatic incidents of his whole life leaped into his mind. All the pleasant experiences and feelings he had ever known were there, too, but were transformed into terror.
A bell was ringing with regular strokes. Across the panel of the mnemonic eraser, the tiny counting lights were alive with movement.