CH. XXVI.] KELATION BETWEEN QUANTITY AND TENSION 



369 



oxygenated blood. The vertical figures represent the percentage 

 saturation of blood with oxygen ; the horizontal figures represent 

 time in minutes. 



It will be seen that at room temperature (A), the rate of oxidation 

 is rapid, but the rate of reduction is very slow. At body temperature 

 the rate of reduction is enormously increased (B); but at body 

 temperature in the presence of carbonic acid the two rates are 

 practically equal (C) ; the amount of carbonic acid employed was the 

 same as that which pervades the body, viz., at a tension of 40 mm. of 

 mercury. This quantity is also approximately equal to that present 



100 



A 



6 10 15 2O 25 3O 

 minutes. 



17 c Free from CO 2 



OS iO t5 2O 25 3O 

 misuses 



37 c Free from C0 2 



O 6 JO /5 20 25 3O 

 minutes. 



37 c 40mm. C0 2 



FIG. 296. Curves showing rate of oxidation and reduction in blood under the conditions described in 

 the text; A, at room temperature (17 C.) ; B, at body temperature (37 C.); C, at body tempera- 

 ture when carbon dioxide at 40 mm. pressure was added to the nitrogen. 



in the alveolar air. The curves show that the rate of reduction is in- 

 creased, but the rate of oxidation is a little lessened. The two curves 

 in C present an extraordinary degree of symmetry, so wonderfully has 

 nature adapted the conditions of life in order that the needs of the 

 body may be served by a substance haemoglobin which by itself is 

 ill adapted for the purpose of oxygen transport. 



In order therefore to understand the dissociation of oxygen from 

 haemoglobin in the body, we must study it, not in a pure solution, 

 but under the more complex conditions actually existing in the body, 



2 A 



