Abstract
Electroencephalograms (eeg) were recorded in normal subjects, who breathed gas mixtures containing from six to eleven volume per cent oxygen for five to seven minutes. Changes of eeg were expressed with mean am-plitude and mean period obtained from the recorded brain waves.
1. Under a high degree of oxygen lack, following changes of eeg were observed. Within a minute after the beginning of the gas breathing, small rapid waves appeared, and corresponding to this change, the mean period was temporarily diminished. Two or three minutes later slow large δ-waves appeared in groups, and the mean amplitude and mean period increased rapidly hand in hand. In the final stage of the gas breathing eeg consisted of almost only δ-waves.
2. In oxygen lack of a slighter degree potentials were markedly sup-pressed at an early stage of the gas breathing, and thereafter the mean period increased prior to the mean amplitude.
3. Soon after the cessation of the gas breathing, δ-waves disappeared, but the normal pattern of eeg was not recovered for a long time. Eeg at the recovery stage were found similar to those obtained in mental fatigue.
