The mental symptoms associated with encephalitis lethargica have been studied recently by Abrahamson[211]. He finds that the patient can be aroused from the initial lethargy and responds quickly and coherently to questions, relapsing again into an apparent sleep. Some irritability is shown. The attitude "expresses a desire to be left alone." If the somnolence disappears it is usually followed by a period of depression. The patient complains of weariness and inability to sleep. Choreic manifestations sometimes occur. The somnolence may terminate, on the other hand, in a profound stupor resembling a drug intoxication with a restless delirium. Even then the patient can be roused momentarily. Responses are automatic with no evidences of emotional disturbance. Flexibilitas cerea is often present. This condition may be followed by a period of confusion, disorientation and amnesia suggesting Korsakow's disease. There is usually a period of mental depression with poverty of thought. Occasional hallucinations were also observed. An exceedingly important contribution to the literature of encephalitis lethargica is an analysis recently made of the symptoms shown in eighteen cases by Kirby and Davis.[212] "The psychic disturbances of epidemic encephalitis present the general characteristics of an acute organic type of mental reaction, corresponding more specifically to a toxic-infectious psychosis. In the acute stages of the disease, psychic torpor and delirium are the most frequently observed mental disturbances although other clinical pictures may be encountered, as the Korsakoff syndrome or more complex mental disorders in which various affective and trend reactions give a special cast to the psychotic disturbance." They report two types of sleep disturbance, hypersomnia and hyposomnia. The former is characterized by drowsiness, lethargy, stupor or coma, depending entirely on the degree reached. In the latter the patient is sleepless at night and somnolent during the daytime. Usually delirium was present at some time in both types of the disease. Often there was a brief period showing a mild depression or anxiety, following lethargy or delirium. Euphoria was observed in a number of instances. In the unrecovered cases they often found residuals—"depressive affects, emotional elevations, irritability, explosive reactions, stubbornness, apathy, etc." Their findings may be summarized perhaps in the statement that "definitely formulated and persistent trends are infrequent in epidemic encephalitis ... we have found much evidence of persisting emotional alteration with little evidence of organic mental defects or dementia."