RESPIRATION 



227 



placed, undiluted and at body temperature, in the saturator, and 

 thoroughly saturated in presence of some of the same mixture of 

 air and CO that the animal had been breathing. The percentage 

 saturations with CO of the haemoglobin in the blood taken 

 straight from the animal, and in that from the saturator, were 

 then determined, and the arterial oxygen pressure calculated in 

 the usual way. The following table shows the results. 



On looking down this table it will be seen that as long as the 

 percentage of CO did not exceed about .03 per cent, or the per- 

 centage saturation of the blood did not go over about 28 per cent, 

 the arterial oxygen pressure was only about that of the alveolar 

 air, assuming that the alveolar air of a mouse has about the same 

 composition as human alveolar air. But as the percentage of CO 

 in the air, or the percentage saturation of the blood, rose, the 

 arterial oxygen pressure rose, first to about that of the inspired 

 air, and then, in most cases, far above it sometimes to double. 



