EFFECT OF TEMPERATURE ON HEMOGLOBIN 183 



reduction from 100 to 94 percent, at 18° C, whilst BC represents the 

 time necessary for the same reduction at 38° C. The former is 35 

 minutes, the latter is 2-5 or, at most, 3 minutes. Had the alteration 

 in the temperature been not 20° C. but 10° C. the ratio of the times 

 necessary to produce the reduction from 100 to 94 per cent, saturation 

 would have been proportional to the square root of (35 ~ 3), i.e. about 

 in the proportion of 3-4 : 1. 



The experiments just described were undertaken by Hill and my- 

 self with some idea of studying the rates of oxidation and reduction 

 of haemoglobin in the sense in which Hartridge and Roughton have 

 carried out the work. Everything that we know, however, suggests 

 that the rate of reduction of the haemoglobin was controlled not by 



C^ 



100 



90 



80 



70 



60 



50 



10 



20 



30 



40 



50 



70 



90 



100 



Fig. 62. Abscissa for rate of reduction =» minutes; for dissociation curve = arbitrary 



unit of pressure. 



the velocity constant of the reduction process, but by the rate of 

 diffusion of oxygen from the fluid into the bubble. What took place 

 is conceived as being somewhat as follows. The pressure of oxygen 

 in the fluid at any moment was that which corresponds, on the oxygen 

 dissociation curve, to the percentage saturation of the haemoglobin 

 at that moment — call this pressure 'p. The pressure of oxygen in the 

 bubble was nil , for only a negUgible amount of oxygen diffused into 

 any one bubble. The rate of diffusion of oxygen from the fluid at 

 any saturation then was proportional to j9 — 0, i.e. to p. 



If that is so it should be possible to reconstruct the dissociation 

 curve in shape, i.e. to plot the percentage saturation against some- 

 thing which is proportional to the pressure. This calculation was 

 attempted with the data given in the two experiments in Barcroft 

 and Hill's paper; the data, however, are not available below 50 per 



