READJUSTMENTS OF REGULATION 29 



To understand the oxygen supply to the body, and the 

 connection between oxygen supply and breathing, it is 

 evidently necessary to understand the circumstances 

 under which oxygen is taken up or given off by the 

 haemoglobin of the blood. These circumstances can 



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Fig. 1. Thick line dissociation curve of oxy haemoglobin 

 in blood in the presence of 40 mm. pressure of CO2. 

 Thin line the dissociation curve of oxyhaemoglobin 

 in blood within the body. 



be investigated outside the body, provided that we 

 are able to reproduce outside the body the conditions 

 which obtain within it. Until recently, failure to 

 appreciate the importance of this led to great error. 



The dissociation of oxyhaemoglobin with fall in the 

 pressure of oxygen can best be represented graphically 

 by a curve; and Figure 1 represents the law of dis- 



