The entire population of the New Jersey State Hospital at Trenton, which is representative of the rural type of general population of the state, has been examined by means of the Wassermann syphilis reaction, in all 1583 individuals being tested. Seventy of these were cases of general paralysis, and 1513 were cases otherwise diagnosed. Of the cases not general paralysis, 1472 reacted negatively and 41 positively, on which basis there is a percentage of 2.7 latent lues in the total hospital population not paresis.Including cases of general paralysis about 7 per cent of all individuals of both sexes examined, and about 10 per cent of all males were found to be infected with syphilis as judged by the serum reaction, and this we take as accurately representative of the entire general adult population of the state of New Jersey.These relatively low figures, as compared with those of some previous more limited investigations in institutions, we believe are solely and wholly accounted for by the type of general population and rural environment from which the individuals examined originally came, and further, that in the differences of environment is found the explanation for the discrepancies in results among these previous investigations themselves.We believe, furthermore, that this investigation, both in itself and by comparison with some of the more reliable previous figures, shows that the relative prevalence of syphilis in city and country is in general exactly two to one.A careful analysis of all data including age, sex, color, nationality, civil condition, and type of psychosis leads to the conclusion that syphilis among the insane is no more frequent in occurrence and differs in no particular of its distribution from that found in any general community; that in fact investigations as to the frequency of syphilis among the insane offers the most convenient method of accurately determining the figures for any corresponding general population, and it is for this reason we state that the prevalence of lues in the entire general adult population of the state of New Jersey is 7 per cent.Only one type of psychosis other than general paralysis (and cerebral lues) has been found to be definitely related to syphilis as cause and effect in either direction. This is the type of focal brain disorder which occurs in middle life as a result of vascular sclerosis. This group was found to constitute 16 per cent of all the arteriosclerotic mental disorders among men and which, although not symptomatically differentiated from other similar focal brain diseases, has an entirely different etiology which may be demonstrated by biological methods.In the field of general paralysis comparison of biological, cytological and chemical findings has pointed out that not only are the processes thus indicated usually found in association, but that there is at least as much evidence for the belief that all are dependent upon one and the same mechanism, viz., the inflammatory process of the central organ, as for the conclusion reached by others that each is separate and independent.Our experience in this series with the original Wassermann technique and that of the Noguchi modification has shown that with alcoholic extract antigen the Wassermann gave a 5 per cent error of deficiency, and the Noguchi a 2 per cent error of excess, and that reliable results are only to be obtained by the use of both methods in combination.Finally, it is believed that with a perfectly controlled material of some 35 cases of purely latent lues with positive serum reaction, it will be possible by future observation and by final autopsy findings to assist in acquiring a more definite knowledge of the significance of the Wassermann reaction in such cases than has as yet been attained.