The pathological changes associated with the arteriosclerotic psychoses are quite clearly demarcated. Clinical differentiations, however, are not so well established. There is some question as to the justification of the separate entities into which Kraepelin would divide the arteriosclerotic processes. For statistical purposes the Association's committee felt that a determination of the frequency of occurrence of the arteriosclerotic group as a whole is all that should be attempted at this time. The following suggestions were offered in the manual as to the delimitations of these conditions:— "The clinical symptoms, both mental and physical, are varied depending in the first place on the distribution and severity of the vascular cerebral disease and probably to some extent on the mental make-up of the person. "Cerebral physical symptoms, headaches, dizziness, fainting attacks, etc., are nearly always present, and usually signs of focal brain disease appear sooner or later (aphasia, paralysis, etc.). "The most important mental symptoms (particularly if the arteriosclerotic disease is diffuse) are impairment of mental tension, _i.e._, interference with the capacity to think quickly and accurately, to concentrate and to fix the attention; fatigability and lack of emotional control (alternate weeping and laughing), often a tendency to irritability is marked; the retention is impaired and with it there is more or less general defect of memory, especially in the advanced stages of the disease, or after some large destructive lesion occurs. "Pronounced psychotic symptoms may appear in the form of depression (often of the anxious type), suspicions or paranoid ideas, or episodes of marked confusion. "To be included in this group are the psychoses following cerebral softening or hemorrhage, if due to arterial disease. (Autopsies in state hospitals show that in arteriosclerotic cases softening is relatively much more frequent than hemorrhage.) "Differentiation from senile psychosis is sometimes difficult particularly if the arteriosclerotic disease manifests itself in the senile period. The two conditions may be associated; when this happens preference should be given in the statistical report to the arteriosclerotic disorder. "High blood pressure, although usually present, is not essential for the diagnosis of cerebral arteriosclerosis."