1184 



PHYSIOLOGY 



pressure of the carbon dioxide. At lower pressures of oxygen, how- 

 ever, the pressure of carbon dioxide makes a considerable difference. 



5/nm 



Q 10. 20 30 



50 60 70 80 96 100 110 420 130 1W 450 



FIG. 495. Effect of varying tensions of C0. 2 on the dissociation curve of oxyhaemo- 

 globin. The lowest curve is the dissociation at a C0 2 tension of 420 mm. Hg. 

 from observations by Barcroft. (BoHR.) 



80 100 



FIG. 496. Dissociation curves of sheep's blood. 



1, normal blood ; 2, blood containing O04 per cent, added lactic acid ; 

 3, blood containing O08 per cent, added lactic acid. 



Thus at an oxygen pressure of 20 mm. Hg. the amount of oxyhaemo- 

 globin formed is 67-5 per cent, at a carbon dioxide pressure of 5 mm., 

 whereas at a pressure of carbon dioxide of 40 mm the amount of oxy- 



