THE NATURE OF HEMOGLOBIN SOLUTION 73 



tap between the haemoglobin and the oxygen above it produces a 

 fundamental alteration in the system for the following reasons : Suppose 

 (1) you have two vessels, A and 5, in which identical solutions of haemo- 

 globin are exposed to identical atmospheres, the atmosphere and 

 the solution being in each case brought into equilibrium with one 

 another; (2) that in ^ a layer of material impervious to oxygen is 

 introduced between the gas and the fluid, whilst in B they are left 

 in free contact; and (3) the conditions are altered so that a little 

 oxygen is displaced from the haemoglobin in each case and goes into the 

 solution. It is contended, and correctly so, that the effect in the two 

 fluids will be different — in A the oxygen will accumulate and produce 

 a greater change of oxygen pressure in the fluid than before, in B, if 

 the atmosphere is large in volume relatively to that of the haemo- 

 globin solution, the concentration of oxygen in the solution will 

 remain approximately unchanged. All this is quite true, but if you 

 are discussing an equilibrium, it is beside the mark. Your equilibrium 

 is made and the third supposition above is that, being made, it is 

 then upset. That supposition is irrelevant and the discussion of the 

 subsequent happenings is in the same category as "the flowers that 

 bloom in the spring." 



Analogies with what happens when a solid (or liquid in which the 

 gas is insoluble) is exposed to a gas at varying pressures of the latter 

 have no bearing on the present equilibrium — such might be calcium 

 carbonate and COg or mercury and oxygen. 



Having eliminated the gaseous phase, the more difficult question 

 arises : Have we a system which consists of a liquid phase composed 

 of water containing oxygen in solution and a solid phase consisting 

 of haemoglobin ; or have we a system which consists of a single liquid 

 phase — the oxygen and the haemoglobin both being in solution? 



The following considerations bear on this point: 



(1) If a "solution" be well and truly made, ultra-microscopic 

 examination reveals no foci which disperse the light, apart from 

 such occasional ones as may be due to contamination. It is, I believe, 

 difficult to detect protein aggregates with the ultra-microscope and 

 therefore this test does not carry us very far. Still, if the test had 

 gone the other way, the presence of "solid" bodies would have to be 

 accepted. 



(2) All "solutions" of haemoglobin maintain an osmotic pressure 

 when dialysed in an osmometer permeable to water and salt, but not 

 to haemoglobin itself. 



