"(a) Simple deterioration: Retention and memory defects, reduction in intellectual capacity and narrowing of interests; usually also suspiciousness, irritability and restlessness, the latter particularly at night. "(b) Presbyophrenic type: Severe memory and retention defects with complete disorientation; but at the same time preservation of mental alertness and attentiveness with ability to grasp immediate impressions and conversation quite well. Forgetfulness leads to absurd contradictions and repetitions; suggestibility and free fabrication are prominent symptoms. (The general picture resembles the Korsakow mental complex.) "(c) Delirious and confused types: Often in the early stages of the psychoses and for a long period the picture is one of deep confusion or of a delirious condition. "(d) Depressed and agitated types: In addition to the underlying deterioration there may be a pronounced depression and persistent agitation. "(e) Paranoid types: Well marked delusional trends, chiefly persecutory or expansive ideas, often accompany the deterioration and in the early stages may make the diagnosis difficult if the defect symptoms are mild. "(f) Pre-senile types: The so-called 'Alzheimer's disease.' An early senile deterioration which usually leads rapidly to a deep dementia. Reported to occur as early as the fortieth year. Most cases show an irritable or anxious depressive mood with aphasic or apractic symptoms. There is apt to be general resistiveness and sometimes spasticity. "(g) Other types." The frequency of senile cases is shown by the fact that of 84,143 admissions to the New York hospitals during a period of sixteen years, 12,017, or 14.2 per cent, were over sixty years of age, while 8.4 per cent were between sixty and seventy years old, and 4.5 per cent between seventy and eighty. Of 49,640 first admissions to the New York state hospitals during eight years 4,724 cases, or 9.52 per cent, were diagnosed as senile psychoses. They constituted 9.63 per cent of the admissions in Massachusetts during 1919 and 10.61 per cent of the 18,336 admissions to twenty-one hospitals in fourteen other states. Of 70,987 admissions to all of the institutions referred to, 6,961, or 9.8 per cent, were senile psychoses.