1906.] Influence of Increased Barometric Pressure on Man. 451 



it is necessary to replace the corks at the bottom of the water bath in 

 Haldane's apparatus by well-fitting rubber ones, as the air is compressed in 

 the corks, which leak at high pressures. Owing to the loss of the water 

 jacket some of our earlier experiments were unsuccessful. Great care is 

 also necessary in readjusting the potash levelling tube, as when the chamber 

 is closed a slight fall of pressure is almost inevitable owing to escape round 

 the washer of the door. 



Haldane and Priestley have shown that the respiration is so regulated as 

 to maintain a constant tension of C0 2 in the alveolar air, which is generally 

 about 5 per cent, of an atmosphere. Now supposing the metabolism to be 

 unaffected by changes of pressure, and the regulation of respiration to 

 continue the same, the amount of C0 2 in the alveolar air must vary inversely 

 as the pressure attained. 



Thus if p be the percentage of C0 2 at normal pressure, then we should 

 have, at two atmospheres, p\ 3 per cent, of C0 2 in the alveolar air. It will 

 be seen that these conditions were almost exactly realised by us. The 

 following table gives the result of two typical experiments. The figures in 

 brackets give the percentages reduced to + lb. in accordance with the 

 above principle. Strictly speaking, the exact height of the barometer should 

 have been recorded, and another correction ought to have been made for 

 charges of temperature in the cylinder. As there is however a necessarily 

 large experimental error, we think it needless to allow for these minor 

 differences, and have accordingly assumed the normal atmospheric pressure 

 to be 15 lbs. to the square inch, and neglected the temperature : — 



Experiment XIV. 10.1.06. Subject, M. G. 



Percentage of CO hi alveolar air. Pressure. 



5-3(5-3) + Olbs. 



0- 9 (54) (Mean of two) + 75 „ 



1- 0(5-0) +60 „ 

 ? 1-3 (5-0) +45 „ 



1- 8(5-4) +30 „ 



2- 7(5-4) +15 „ 

 5-4(5-4) + „ 



Experiment XV. 10.1.06. Subject, L. H. 



Percentage of CO„ in alveolar air. Pressure. 



4- 7(4-7) + Olbs. 

 0-9(4-5) . +60 „ 

 0-7 and 0-8 (4-5*1 +75 „ 



0- 95 (4-75) +60 „ 



1- 2 (4-8) +45 „ 



1- 8(5-4) +30 „ 



2- 5 (5-0) +15 ,. 



5- 0(5-0) + „ 



