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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Wenseess 
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8 9 10 “ 12 3 “4 is 16 7 
3 4 s 6 7 
Prassurs of oxygen a percentage of cue abmotth 
Fic. 1. Thick line—dissociation curve of oxyhaemoglobin 
in blood in the presence of 40 mm. pressure of COs. 
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- 
