RESPIRATION 105 



persons who inhabit very high parts of the earth develop a greatly- 

 increased chest capacity. 



Addendum. The account given in this chapter of the manner in 

 which CO2 is carried by the blood represents what I have taught 

 for many years, and is largely based, as mentioned above, on the 

 teaching of Pfliiger and Zuntz. A very different view of the 

 subject has recently been presented by Buckmaster, Bayliss, and 

 others. According to this view the extra COg taken up in the 

 venous blood is combined, not with alkali, but with haemoglobin, 

 and may also be in part adsorbed by haemoglobin and other 

 proteins. As evidence that haemoglobin and other proteins do 

 not play the part of weak acids in expelling CO2 from its combi- 

 nation with alkali, Buckmaster cites experiments in which he 

 found that, contrary to Pfliiger's statement, blood or haemo- 

 globin is not capable of expelling CO2 from a weak carbonate 

 solution in the vacuum of a blood pump at body temperature.^ 

 It seems to me that these experiments were fallacious because the 

 blood was neither boiled nor shaken. Boiling, shaking, or bubbling 

 is necessary to remove the COg. When Pfliiger's experiment was 

 repeated in a simple form by Adolph in my laboratory the ex- 

 pulsion of CO2 from sodium carbonate by blood was found to 

 occur quite readily.^ As already mentioned, Buckmaster's con- 

 tention that haemoglobin gives a characteristic spectrum with 

 CO2 was also found to be incorrect. 



The supposition that an extra amount of gas is adsorbed by the 

 proteins of blood has no basis. The careful experiments of Bohr 

 and other previous observers show clearly that apart from chemi- 

 cal combination blood takes up, not more, but considerably less, 

 gas than an equal volume of water. The only apparent exception 

 to this rule was the fact that oxygenated blood (but not reduced 

 blood) yields slightly more nitrogen than the quantity calculated 

 from its estimated solubility. The existence of this small surplus 

 Avas confirmed by Buckmaster and Gardner.* The apparent surplus 

 is almost certainly due to what is a rather common source of 

 slight error in gas analysis. When the gas pumped off from oxy- 

 genated blood is analyzed, the first step is to bring the gas into 

 contact with potash solution to absorb the CO2. When this is ab- 

 sorbed a gas mixture consisting almost wholly of oxygen is left 

 in contact with the potash solution. But the latter is saturated 



* Buckmaster, Journ. of Physiol., LI, p. 105, 1917- 



'Adolph, Journ. of Physiol.. LIV, Proc. Physiol. Soc. p. XXXIV, 1920. 



* Buckmaster and Gardner, Journ. of Physiol., XLIII, p. 401, 19 12. 



