Diefendorf[279] states that manic-depressive insanity comprises from twelve to twenty per cent of the admissions to hospitals for mental diseases. He reports defective heredity as being shown in from seventy to eighty per cent of the cases. He also found about seventy-five per cent of the patients suffering from this disease to be of the female sex. Buckley[280] states that sixty per cent of the cases give positive histories of "familial neuropathy and psychopathy." Paton[281] is of the opinion that heredity is a factor in from eighty to ninety per cent of all cases. Hoch has called attention to the constitutional makeup of individuals subject to manic-depressive attacks and suggests that they are usually of a moody, morose type, unduly optimistic or temperamentally unstable. Kraepelin[282] found suicidal tendencies in 14.7 per cent of the female patients, and in 20.4 per cent of the men. Nine per cent of his cases showed a manic makeup; 12.1 per cent, a depressive temperament; 12.4 per cent were irascible or nervous; and from three to four per cent exhibited cyclothymic tendencies. Of the cases admitted to his clinic 48.9 per cent were depressive forms; 16.6 per cent, manic; and 34.5 per cent represented both types in various combinations. Melancholia simplex and gravis constituted 23.5 per cent of the simple forms, 13.5 per cent showed phantastic delusions and 6.1 per cent anxieties. Hypomanias made up four per cent, and acute mania, 9.8 per cent of the cases. Confused and stuporous states constituted 8.2 per cent and compulsions, one per cent. Lighter forms constituted ten per cent, and more severe types, nine per cent of the admissions. Stupors and clouding were found in 4.9 per cent and delusional states in 4.9 per cent of the total. He quotes Walker as reporting, in a study of 674 cases, that excitements contributed eleven per cent; depressions, 55.7 per cent; and circular forms 33.3 per cent of the male cases; and excitements, 6.2 per cent; depressions, 70.2 per cent; and circular types, 23.6 per cent of the female admissions. In from sixty to seventy per cent of Kraepelin's cases the first attack was a depression. In two-thirds of them, after the first mild attack there was a remission. In one-third of the cases, the depression terminated in an excitement followed by recovery. When the disease begins with a manic attack, two-thirds of the cases are followed by a remission. He reports excitements with a duration of ten years and depressions of fourteen years standing. In a study of 703 remissions he found ninety-six lasting from ten to nineteen years; thirty-four, from twenty to twenty-nine years; eight, from thirty to thirty-nine years; and one of forty-four years. He is of the opinion that the length of remission bears no relation to the duration of the attack. Of the depressions, 167 had a remission of six years; forty-six of 2.8 years; and twenty-seven of two years or more. Of the manic forms, fifty-three