122 HEMOGLOBIN 



a small range of molecular attraction and a mono-molecular adsorbed layer, using 

 well-established equations of the kinetic theory; and the author also gives a deriva- 

 tion of the "adsorption isotherm " on theoretical grounds. It would seem undesirable, 

 however, to use the form of the relation between amount adsorbed and concentration 

 as a criterion of adsorption, for this relation can never be a very simple conception, 

 depending as it does on so many factors; but nothing could be simpler than to con- 

 ceive of a surface as possessing either localised or diflFuse attraction for a substance 

 it takes up. It may be that in some instances it is not yet possible to form any 

 estimate of the fraction of the surface covered; yet as accurate knowledge of the 

 dimensions of molecules and of their orientation on surfaces accumulates, the ap- 

 plicability of the criterion here suggested will increase. I have tried to show, however, 

 that it is already more generally applicable than any other. 



N. K. Adah. 



The University, Sheffield, March 6. 



Conant's theory. Though out of its chronological order, mention 

 may be made here of a recent paper by Conant and Scott (4). 

 These authors, impressed with the view that nitrogen appears more 

 soluble in blood than it is in the amount of water which blood con- 

 tains, have revived the adsorption theory, or rather have combined 

 it with the theory of chemical combination. In their view the in- 

 flection is caused by an increase in the concentration of the oxygen 

 around the haemoglobin molecule, so that at low pressures the actual 

 pressure of oxygen in contact with the haemoglobin is greater than 

 the pressure throughout the fluid generally. 



The evidence in favour of oxy- and carboxyhaemoglobin being 

 chemical compounds, is in fact of just the same nature as that of 

 any other substance which exists as the results of a balanced action. 

 Granting then the chemical nature of the union let us turn to the 

 theories which treat of it on a chemical basis. 



Hiifner's theory (5) is the simplest of these and assumes the reaction 

 to be a unimolecular one : 



Hb + Oo :^ HbO 



I say "assumes" advisedly because Hiifner never was at pains to 

 prove his theory except in one respect. Though he pubUshed a dis- 

 sociation curve, the curve was obtained from theory and not the 

 theory from the curve. Hiifner never determined the curve from a 

 series of points. He assumed that the equation was as stated and 

 therefore that equilibrium would be represented by the equation 



[Hb] [O2] = K [HbO^]. 



