CHAPTER IV 



THE EFFECT OF ELECTROLYTES ON THE AFFINITY OF 

 HAEMOGLOBIN FOR OXYGEN 



UP to the present we have made no attempt to treat of the work, 

 which has recently been carried out on the affinity of haemoglobin for 

 oxygen, on any sort of chronological basis, and now, having arrived at 

 the fourth chapter we have also arrived at the point at which much 

 of the work discussed in the preceding pages really began, and from 

 which it proceeded always from the point of greater complication to 

 the point of greater simplicity. It was the constant effort to unravel 

 a knot which gave us the threads from which ultimately to weave a 

 fabric. 



What we wished to do may sound simple. In practice it has 

 proved to be quite the reverse. It was to calculate the oxygen 

 pressure in the capillary circulation. 



We were therefore face to face with the problem of whether it 

 was possible from the percentage saturation with oxygen of a given 

 sample of blood to calculate from the dissociation curve of blood the 

 oxygen pressure to which the blood was exposed. This was our first 

 practical introduction to the dissociation curve. When we consulted 

 the literature of the subject we found that each paper brought our 

 ideas into a state of greater complexity. The authors who had 

 written most recently on the subject were Zuntz' 1 ', Loewy (2) , Bohr (3) , 

 and Franz Miiller (4) . Zuntz and Loewy had made the important con- 

 tribution that apparently no two samples of blood, whether from man 

 or beast, could be relied upon to have the same dissociation curve. 

 Their view had been supported by Bornstein and M tiller who worked 

 on cat's blood, whilst Bohr and his colleagues had stated that this 

 was in large part due to the fact that the dissociation curve is very 

 sensitive to the presence of carbonic acid ; their observations were 

 discounted or neglected by many authors. Mtiller, however, had also 



