When we leave the subject of heredity we are on much more certain ground. There is no question whatever as to the rôle played by traumatism, senility, arteriosclerosis, syphilis, brain and nervous diseases, alcoholism, exogenous toxins, epilepsy, pellagra and somatic diseases in the causation of mental disorders. In an analysis of 4,079 cases examined at the Munich Clinic, Kraepelin[70] found the following factors involved:—1. Physical diseases, infections and gross brain lesions, 1.3 per cent; 2. Syphilis and metasyphilis, 10.3 per cent (general paresis 9.4 per cent); 3. Toxins—alcohol, morphine, cocaine, etc., 22.8 per cent (alcoholic psychoses 22.4 per cent); 4. Traumatic neuroses and prison psychoses, 2.5 per cent; 5. The presenile and senile psychoses, arteriosclerosis, etc., 5.6 per cent; 6. Dementia praecox, epilepsy, idiocy and imbecility, 27.2 per cent; 7. Psychopathic and hysterical states, and manic-depressive insanity, 30.3 per cent. Conditions existing in our hospitals and clinics are somewhat different. As the result of a study of over seventy thousand first admissions to forty-eight hospitals in sixteen different states we are now in a position to speak quite definitely as to the frequency of the conditions above referred to as etiological factors. Traumatic psychoses quite uniformly represent a little less than one-half of one per cent of the admissions to our institutions. The senile psychoses constitute approximately ten per cent and arteriosclerosis five per cent of the total. General paresis averages about twelve per cent in the New York hospitals and from seven to ten per cent in the other states. Cerebral syphilis amounts to a little less than one per cent of the cases. It should be said that in the large cities the rate for syphilis is, in some instances at least, twice as high as that given. Brain tumor, with all other brain and nervous diseases, only constitutes about one and one-half per cent of our admissions. Alcoholism, which has been responsible for as high as ten per cent of all admissions, from time to time, has been decreasing gradually during the last five years and in New York in 1920 constituted less than two per cent. Epileptic psychoses in our state hospitals amount to from one to two and one-half per cent of the total. As a general rule pellagra is not a factor of any consequence, amounting to less than one-half of one per cent of the admissions. In a few of the southern hospitals large numbers of pellagra are encountered. The psychoses accompanying somatic diseases are represented by from three to four per cent of the whole number. In addition to this, there is still a considerable number of cases reported from the hospitals as being caused by psychic trauma of various kinds. These represent the acute psychoses usually resulting from mental and emotional upsets but with nothing which definitely points to constitutional disorders or hereditary influences.