Never until very recently has any great importance been attached to the psychoses due solely to age or much interest manifested in them. These forms of insanity in the majority of our textbooks have appeared only under the designation of senile dementia. This is true of the earlier editions of Krafft-Ebing and many other writers. Clouston referred to senile dementia as one of four varieties of mental enfeeblement. "Most cases,"[156] he says, "fall under three varieties. The first has as its chief characteristics depression and lethargy. The second consists chiefly of excitement, sometimes with a certain exaltation, but always with irritability, restlessness, unreason, suspicion, and change of affection. The third variety consists chiefly of the abolition of mind in all its forms, or senile dementia, and of complete dotage. In some cases those three varieties form three different stages in the same case. In others they do not change." Régis, in a work on mental medicine covering 668 pages in all, devoted two and one-half pages to a consideration of the insanity of old age. Ziehen[157] in 1894 included "dementia senilis" with general paralysis, epileptic, alcoholic and terminal deteriorations in his group of "acquired defect psychoses" and characterized it as "a chronic organic psychosis of advanced years, the principal symptom of which is a progressive intelligence defect." Excitements, depressions, confusional states, deliria, deteriorations, mental mechanisms of any and all kinds, occurring late in life, were usually disposed of without any effort at differentiation by the very convenient method of relegating them to the obscure domain of senile dementia. This is a field which on exploration has been found to be one of considerable interest. It has been pointed out that manic-depressive insanity not infrequently occurs in persons of advanced age. Uncomplicated alcoholic psychoses are not at all rare. Bleuler has advanced the theory that dementia praecox and certain of the senile conditions are similar if not identical processes. General paresis has been demonstrated in the later periods of life by modern laboratory methods and the diagnosis confirmed at autopsy. Cerebral syphilis certainly cannot be left out of consideration. Toxic deliria are encountered now and then. Even the psychoneuroses are possibilities.