BLOOD 



493 



fc 



EDIK 



Hb \oo% 



The amount of oxygen taken up and given off is not 

 proportionate to the partial pressure of the gas to which the 

 Hb is exposed. 



This has been ascertained by exposing solutions of Hb to 

 atmospheres with ditterent percentages of oxygen, i.e. to 

 oxygen at different pressures. 



Starting from an atmosphere containing no oxygen — with 



TbTALH ^ 100 Dissociation Curve of Hcmoglobin at ST'C. 



100 



90 

 80 . 



o 

 70 i 



o 



50 1 

 40 f 

 30 ^ 



20 (±e 



10 



13 



28 



45 



63 



100 



94 

 87 



72. 

 55 

 37 



Dissociation Curve ofH/EMOglobin inthe3lood. 



Fig. 200. — The Dissociation Curve of Ha;moglobin in pure solution (continu- 

 ous line) and in blood (broken line). The oxj-gen pressure in mm. is 

 indicated by the ordinates, and the percentage saturation is 

 indicated by the absciss*. Note the more rapid dissociation under 50 

 mm. Hg in blood than in pure solution of Hb. 



no partial pressure of oxygen — it is found that the Hb is 

 entirely reduced— carries no oxygen. When exposed to 

 atmospheres containing higher and higher percentages of 

 oxygen it is found that the amount taken up rapidly 

 increases till at 30 mm. Hg, equivalent to about 6 per 

 cent, of oxygen in the atmosphere at sea-level, the Hb is 

 saturated to about 80 per cent. 



