Influence of Variations of O 2 and CO 2 Tension in Inspired Air Upon After-images

Abstract

It was our objective to study the influence of variations of O₂ and CO₂ tension upon a simple and quantitatively measurable visual process in man. We chose the latent period of a negative afterimage. The experimental subject fixated with both eyes the center of a yellow square on a grey background at a distance of 60 cm. The eyes were closed for one minute prior to each experiment. After a fixation time of 10 seconds the eyes were closed and a stop watch started. When the negative after-image appeared the watch was stopped. Control experiments showed that after a period of training the latent periods were very constant if the intervals between the individual experiments were at least 10 minutes. Fifty-five experiments were performed with 5 subjects. In the first group the influence of O₂ lack was studied by allowing the experimental subject to breathe various air-nitrogen mixtures from 7 to 30 minutes. The O₂ concentration varied between 9.2% and 16.0%. Whereas a reduction of the O₂ concentration to 13% was without influence on the latent period of negative after-images, very considerable changes occurred after breathing 9-11% O₂ for various times (7-27 minutes). The latent period was either considerably lengthened or became infinite since the after-image disappeared. In those experiments in which a negative after-image appeared, the subject noticed a decrease in its intensity. In some cases the latent period of the after-image remained lengthened even 10 minutes after the end of the breathing period. The subsequent experiments showed approximately the same latent periods as before the O₂-lack experiment.