RESPIRATION 



233 



-dredths cc. of this blood was then introduced into the saturating 

 vessel in the manner described in our paper. Immediately after- 

 wards two further small samples of blood were taken from the 

 subject's fingers — as a rule one from each hand — the blood being 

 received into small test tubes quite full of water, which were im- 

 mediately corked. These samples served for the colorimetric 

 determination of the degree of saturation of the blood with carbon 

 monoxide. A last sample of the inspired air was then taken, and 

 a sample of the alveolar air. Breathing into the apparatus was 

 continued for about two minutes in case the composition of the 

 air in the respiration apparatus had been altered by the deep ex- 

 piration necessary to afford the alveolar air sample : some car- 

 bonic acid, for instance, might have got through the caustic soda 

 tin. The experiment then terminated, and the mouthpiece of the 

 respiration apparatus was at once closed. The saturating vessel 

 containing the blood was as soon as possible filled by displacement 

 with some of the air remaining in the respiration apparatus, which 

 was expelled for this purpose from the bottle E by the arrange- 

 ment indicated at P and R. While the saturating vessel was being 

 rotated in the water bath at 38° the determination of the degree 

 of saturation with carbon monoxide of the samples taken from 

 the fingers was proceeded with. During this time also the analyses 

 of the alveolar air, and air from the respiration apparatus, were 

 completed and when necessary the analysis of a sample from the 

 saturating vessel. After the saturating vessel had been rotated for 

 half an hour or more, it was removed from the water bath and 

 the degree of saturation with carbon monoxide of the blood con- 

 tained in it was determined. All the data for calculating the 

 oxygen pressure of the arterial blood and contrasting it with that 

 of the alveolar or of the inspired air were then at our disposal. 



Our first experiments on man were taken up with determining 

 the arterial oxygen pressure under as normal conditions as pos- 

 sible, and we especially wished to guard against the effects of 

 deficiency of oxygen. We therefore employed a low saturation 

 (23 per cent) of the blood with CO and made sure that the res- 

 piration apparatus contained a normal atmosphere by ventilating 

 j^ it freely with fresh air before the experiment. All the experiments 

 were made with the subject sitting at rest. 



The results of these experiments are collected in the accom- 

 panying table. 



The figures show quite distinctly that under normal circum- 

 stances when the subject is at rest the arterial oxygen pressure in 



