Psychoses due to various gases are occasionally encountered. Illuminating gas is a rather common means of suicide, as is shown by the newspapers. It has been found that the cause of death in these cases is carbon monoxide, which is also often reported as responsible for the asphyxiation of workmen in garages and other places where gasoline motors are used. This occasionally results from the improper ventilation of laundries, engine rooms, gas plants, iron foundries, etc. These conditions have been very fully studied by O'Malley.[240] The mental disorders due to carbon monoxide are described as being characterized by a sudden attack of confusion and clouding associated with a period of complete amnesia. There may be disturbances of attention and Korsakow's psychosis is sometimes strongly suggested, with memory impairment and tendencies towards fabrication. This condition may be transitory or last for many months. On recovery the patient usually has no recollection of any events taking place after the time of the poisoning. Immediately following the initial unconsciousness there may be excited periods or delirious states with aphasic disturbances. In chronic cases delusions of persecution are often observed. The psychosis frequently does not develop until several weeks or months after the actual poisoning. Several observers have referred to a mask-like expression of the face, with emotional indifference, apathy and outbursts of laughter. The mood has been described as characterized by emotional instability. O'Malley calls attention to the important fact that the mental disturbance may have been the cause of suicidal attempts rather than a result of the gas poisoning. Confused delirious states due to carbon monoxide poisoning, also conditions resembling Korsakow's disease, have been described by Kraepelin. Several cases somewhat similar to that described by O'Malley have been observed at the Boston State Hospital. An analysis of the statistics of American institutions shows that psychoses due to drugs and other exogenous poisons are quite rare in this country. They represented only .39 per cent of the admissions to the New York state hospitals during a period of eight years. The number admitted to Massachusetts hospitals is still less. In a total of 70,987 first admissions to forty-eight hospitals in sixteen different states there were only 324 cases due to exogenous poisons. This constituted .65 per cent of the total number admitted. It is interesting to note that during a period of eight years, when 49,640 cases were admitted to the New York state hospitals, 154 cases of psychosis due to opium or morphine were reported, five due to metallic poisons, eighteen caused by gases, and nine of types unspecified. No case of uncomplicated cocainism was reported during that period of time.