VOLUNTARY BREATHHOLDING. II. THE RELATION OF THE MAXIMUM TIME OF BREATHHOLDING TO THE OXYGEN TENSION OF THE INSPIRED AIR'

The striking effect of 100 per cent oxygen in lengthening the period of voluntary breathholding became apparent to us during experiments con-cerned with underwater weighing, in which it was desirable for the subjects to remain immersed as long as possible. Although a few observers (1, 2) have noted this effect of oxygen previously, it has received very little attention in the literature since World War I; and some, notably Schneider (3), concluded that oxygen had a relatively insignifi-cant influence upon the breathholding time. The studies reported herewith were originally presented (4) as a method for demonstrating ob-jective physiological effects of relatively small changes in altitude (PO2, oxygen tension). Thi