

Rates of oxidation and reduction of blood 177 



upper portion of the curve of reduction is steep whereas the upper 

 portion of the oxidation curve is not steep but gradual. If these 

 curves give a true picture of the time relations of oxidation and 

 reduction in the body, it would seem that the blood is much more 

 rapidly reduced in the tissues than it is oxidised in the lung. 



This check made me anxious to pursue the matter and find out 

 just what portion of each curve was involved in the ebb and flow 

 of respiration. Data were required, firstly as regards the curve of 

 oxidation. It is probably true that the blood in the lung of the 

 resting person is exposed to an oxygen pressure of about 100 mm., 

 and therefore that I was justified in using the curve of oxidation 

 as given. But does the blood become saturated up to the point of 

 being in equilibrium with this pressure ? This is a point on which 

 the most diverse views are held by physiologists, who have estimated 

 the percentage saturation of the arterial blood at various figures from 

 88 per cent, upwards. 



The variety of the estimates is no doubt a measure of the difficulty 

 of obtaining an accurate experimental procedure for the determina- 

 tion of the facts. They are based upon various experiments on 

 animals in which the respiration was probably upset to some extent, 

 either in one direction or the other. 



The only obvious way of getting at the percentage saturation in 

 the arterial blood was to get some person who would submit to 

 having a cannula put in an artery as he sat in a chair in his usual 

 health. Some of the arterial blood could then be withdrawn without 

 coming in contact with air, and analysed. It chanced that shortly 

 after (Minima's experiments my path crossed that of such a person. 

 Arthur Cooke (2) decided on the extreme measure of performing the old 

 operation of transfusion. The patient was transfused from the radial 

 artery of his sister and I am indebted both to the surgeon and the 

 lady for allowing me to collect a sample of arterial blood at the end of 

 the operation, which proved to be 94 per cent, saturated with oxygen. 

 In my attempt to discover how much of the oxidation curve was in- 

 volved in the process of respiration, I took Fig. 93 c. as my starting 

 point. I marked the curve at the point of 94 per cent, saturation and 

 blackened from here downwards. The next question was where to stop. 

 To this question there is no definite answer. In different organs the 

 blood becomes reduced to different degrees. I should like to draw a 

 diagram for each organ in the body. But for the present let me 

 suppose that on the average half of all the oxygen which blood can 



B. R. F. 12 



