Acute mania is not uncommonly mistaken for general paralysis, when, as often happens, the delusions are as expansive and the tremor as great in the mania as in general paralysis; and it may be several months before the differential diagnosis can be made with certainty. In the presence of a high degree of maniacal excitement, with great emotional agitation and muscular tremor, it is difficult to establish the fact of the existence or not of dementia in doubtful cases until it is well developed. Acute mania has been known to constitute the prodromal period of general paralysis for a number of years. Primary mental deterioration cannot be always differentiated from general paralysis of the demented type in its early stage. After the {200} age of sixty the probabilities are in favor of primary mental deterioration in doubtful cases, but general paralysis occurs—seldom, to be sure—up to the age of sixty-five. Early senile dementia may simulate general paralysis of the subacute form, but has not its clinical history. General paralysis of the quiet, insidious type and primary mental deterioration have been called premature senility. The three diseased conditions have certain points of similarity, and the pathological processes involved in them do not differ sufficiently to authorize the assumption that they are not closely related, if not simply variations, due to age and other causes, in one morbid process. Finally, the mental impairment caused by the prolonged use of bromide of potassium and hydrate of chloral has been mistaken for general paralysis, until a critical examination unmistakably showed the presence of the well-known symptoms of those drugs. In examining the patient it is especially important to avoid leading questions, as in general paralysis and in those conditions which simulate its early stage the mind is in a condition to readily fall into the train of thought suggested to it. The fact should be kept in mind, too, that the symptoms in early general paralysis are so variable as to be sometimes quite evident, and at other times not to be got at with certainty at all or only after long and patient examination; that they sometimes quite disappear under the influence of complete mental and bodily rest; and that in all stages, until near the end, such complete remissions may occur as to make the diagnosis, independent of the history of the case, difficult if not impossible.