Dr. Prentice said that syphilis, in its incidence, diagnosis and treatment, presented, in mental hospital practice, problems which differed from those met with in dealing with the disease in general practice and in V.D. clinics. In the former its incidence was higher than in the general population, and that was largely because many of those whose nervous system had become affected by the later stages of the infection ultimately developed a psychosis. Drugs which were efficacious in somatic syphilis showed but little therapeutic effect in the treatment of the nervous system when affected by syphilis. There was a wide variation in the syphilis occurrence-rate among new admissions to mental hospitals, namely, from 5% to 31%; there was no doubt that incidence varied in different parts of the country; for instance, at Whittingham Mental Hospital, Lancashire, the male admissions in one year showed 21–9% with syphilis, and females 8–9%. At Narborough in the past two years—using the same methods of diagnosis—the positive males were only 7–7%, the females 4–6%. It was difficult to estimate reliably what proportion of the general population suffer from syphilis, but comparison of the figures of the Royal Commission on Venereal Diseases with those given by numerous workers in mental hospitals—excluding cases of general paresis and meningo-vascular syphilis—showed that the part played by syphilis in the ætiology of ordinary mental diseases must be a very small one. Bearing in mind the body-mind relationship, any toxic or infective process which could be a factor in the ætiology of mental illness should be dealt with. Even if the disease were predominantly psychogenic, all possible physiogenic factors should be eliminated or dealt with.