RESPIRATION 87 



carbonate is expelled in the vacuum pump, and can be recovered 

 in the gaseous form with the help of the perfect vacuum of the 

 Pfliiger blood pump.* This can now be easily understood in terms 

 of the theory just stated. The blood must be either boiled or 

 shaken : otherwise the disengagement of CO2 is excessively slow. 



When serum alone, and not whole blood, is exposed to the 

 vacuum of the pump, most of the CO2 can be pumped out, but not 

 quite all. It is necessary to add some acid in order to obtain the 

 whole of the CO2 — at any rate within any reasonable time. The 

 proteins of the serum are not present in sufficient amount to effect 

 the dissociation of the whole of the sodium carbonate, but the ex- 

 pulsion is easy when the haemoglobin of the corpuscles is added. 

 Both haemoglobin and serum proteins act towards sodium carbon- 

 ate as acids, and it was shown by Sertoli^ that much of the CO2 

 can be expelled in the pump from sodium carbonate solution if 

 serum proteins are first added. 



Bohr found that haemoglobin solutions, even if they are first 

 rendered slightly acid, will combine with considerable amounts 

 of CO2, and he was thus led to what seems to me to be the er- 

 roneous conclusion that haemoglobin has a specific power, apart 

 from its alternative acid or basic properties, of combining with 

 CO2. Equally erroneous, as Priestley^ has recently shown, is a 

 similar conclusion which was put forward on spectroscopic 

 grounds. 



We have already seen what predominant physiological im- 

 portance is attached to the pressure of CO2 in the arterial blood, 

 and with what exactitude this pressure is regulated. We should 

 therefore expect to find that the pressure of CO2 in the tissues of 

 the body generally is of the same importance and subject to simi- 

 lar regulation. To understand this regulation it is of primary 

 importance that we should know the laws of dissociation of CO2 

 from its combination in blood. Until quite recently our knowledge 

 on this subject was very limited, although Bohr''^ had constructed 

 a tentative dissociation curve from observations partly by Jacquet 

 and partly by himself, on samples of blood from the ox and dog. 



The matter was taken up a short time ago by Christiansen, 

 Douglas and myself^ with the help of the new method of blood- 



* Pfliiger, Ueber die Kohlensdure des Blutes, p. 6, 1864. 

 'Sertoli, Hoppe-Seyler's Med.-Chem. Unlets., Ill, p. 356, 1868. 

 "Priestley, Journ. of Physiol., LIII, Proc. Physiol. Sic, p. LVIII, 1920. 

 'Bohr, Nagel's Handbuch der Physiol., II, p. 106, 1905. 



• Christiansen, Douglas, and Haldane, Journ. of Physiol., XLVIII, p. 244, 

 1914. 



