Penicillin has excited the whole world. It has done for the common bacterial infections what the sulphonamides had done for meningococcal meningitis and quinine for malaria. But penicillin was an antibacterial remedy: it was not to be expected that it would be potent against the protozoal infection of syphilis. Moreover it was soon discovered that penicillin given intramuscularly did not find its way into the cerebrospinal fluid; it did not, it was said, pass the blood-brain barrier, and so it was inherently improbable that it would have much effect on syphilis of the nervous system. Moreover, we knew that nowhere did the spirochete become more strongly entrenched than in the brain. It was, therefore, right and natural that the first rumours that penicillin was in some degree effective in cases of neurosyphilis, and even in cases of general paralysis of the insane, should be received with a certain amount ofincredulity, and this attitude is apparent in most of the reports on the trials of penicillin in neurosyphilis, for nearly all observers, finding some clinical improvement but little immediate change in the cerebrospinal fluid and blood, have gone on to treat their patients with malaria.Early Personal Experiences My own attitude at the beginning was the same. Just at the time when penicillin first became available for civilian use, a man of 50 suffering from taboparesis was admitted to the National Hospital, Queen Square, and came under my care. He was euphoric and fatuous, and had recently lost his position as accountant in a small firm. He-was pursuing allotment gardening in a hypo-manic way, and had undertaken several allotments though he was a small, weak man. At home he was restless,