358 



THE RESPIRATION 



Fig. 125. Fridericia's apparatus for measuring the CC>2 in alveolar air. The person expires 

 forcibly through the tube with the stopcocks as in I. A is closed and the tube placed in water to 

 cool the air, after which B is turned as in II. The entrapped column of air equals 100 c.c. A 

 solution of caustic alkali is now sucked into C with stopcocks as in II. B is then turned as in 

 I but with A still closed, and the alkali solution allowed to enter b, after which B is turned off, 

 the excess of alkali solution in C allowed to run. out and the burette shaken. The burette is 

 then submersed up to a in a cylinder of water, with B as in III. After allowing for cooling, 

 the level at which the water stands gives the per cent of CO^. 



20 $9 



in, inspired 

 air 



Co* 



130 to 50 



30 



Fig. 126. Curves to show the relationship between the O 2 and CO 2 tensions in alveolar air 

 (dotted lines) and arterial blood (continuous lines). It will be observed that the tension of CO 2 

 in blood is slightly above that in alveolar air, but that the reverse relationship obtains for O 2 . In 

 the upper part of the curve the Q-> tension in the alveolar air was experimentally altered, causing 

 a corresponding alteration in the 6 2 tension of the blood. ' This result is of practical significance 

 in connection with O 2 alterations in gas poisoning, pneumonia, etc. (From A. and M. Krogh.) 



