Rates of oxidation and reduction of blood 175 



Through the experiment which I shall describe we have adhered to 

 this pressure of oxygen for the oxidation. 



The above experiment lives in my mind as being one of the most 

 instructive with which I have had to do. Consider the task which 

 is set to Nature in providing a medium for respiration a medium 

 which is at one moment in the lung acquiring oxygen, at another in 

 the tissue imparting the amount it has acquired. Think, too, that the 

 blood must be prepared to yield up its oxygen in a space of time of 

 the same order as that in which it acquires the oxygen. Then turn 

 to Fig. 92 and think of the rapidity with which the haemoglobin 

 acquires its oxygen in the experiment and the tenacity with which it 

 holds to the gas. I believe the haemoglobin would have gone bad 

 before it had become reduced under the conditions of this experi- 

 ment. Truly Nature has been set a wellnigh hopeless task. 



But with the advent of the salts the process of reduction becomes 

 much more easy, as is shown by the work of Oinuma (1) , who com- 

 menced his research by performing the experiment on blood instead 

 of haemoglobin solution. Here also (Fig. 93 A) the rate of reduction 

 of the blood is slow out of all proportion to the rate of oxidation ; 

 still the disparity is not of that apparently hopeless character which 

 it assumes in the case of the dialysed haemoglobin solution. 



The results of Oinuma's experiments turned out to be intensely 

 interesting. They were as follows : 



The rate of reduction was increased 



(1) by the addition of C0 2 to the reducing gas, 



(2) by the elevation of temperature. 

 The rate of oxidation was retarded 



(1) considerably by the addition of C0 2 to the oxidising gas, 



(2) to a very slight extent by elevation of temperature. [It 

 should be stated explicitly that this statement does not actually imply 

 a diminution in the velocity constant of the reaction Hb + O 2 > Hb0 2 , 

 for reasons given in Oinuma's paper.] 



The effect of these factors will be seen at once from Fig. 

 93 A, B, c. In the first there is no symmetry in the relation 

 between the rates of oxidation and reduction. The oxidation takes 

 place with much greater rapidity than the reduction. But as the 

 conditions of the experiment approximate more and more closely 

 to those of the body, the rates of oxidation and reduction become 

 more and more nearly equal until at last, when the conditions of the 

 body are imitated as closely as is possible, the curves which represent 



