CHAPTER VI 



SPECIFIC OXYGEN CAPACITY 



Xhe specific oxygen capacity is the relation of the oxygen to the 

 iron in haemoglobin. Its interest lay at first in its relation to the question 

 of whether or no there was more than one kind of haemoglobin. On 

 other grounds it is agreed that there are innumerable kinds of haemo- 

 globin, the protein in each being specific to the organism. When 

 I wrote the original edition of The Respiratory Function of the Blood, 

 the specific oxygen capacity of haemoglobin was again on the tapis. 

 The question then was : Is oxygen united chemically to haemoglobin 

 or is the union one of adsorption? Here again it seems to me that 

 opinion has crystallised. In this country, as far as I know, Bayliss(i) 

 was the last writer who sympathised with the view that oxyhaemo- 

 globin was purely an adsorptive compound. I do not know of any 

 such in America and, in Europe, if there are they, like Bayliss, are 

 persons whose interest is rather in adsorption than in haemoglobin. 



We have now reached a yet higher plane. The question in front of us 

 is as follows : When haemoglobin is present, to what extent are other 

 iron-containing bodies present also? We have stated the view that 

 haemoglobin is only maintained in statu quo as part of a mass action 

 which involves haemochromogen and that haemochromogen itself only 

 exists in the presence of reduced haematin(2). Of these three sub- 

 stances, haemoglobin, haemochromogen and reduced haematin, only 

 one, haemoglobin, contains oxygen which can be abstracted in the 

 free state by ferricyanide or by a vacuum, whilst all three contain 

 iron. It follows, therefore, that more iron must be present than is 

 equivalent to the oxygen. The question is: How much more iron? If 

 the ratio of iron to oxygen is not considerably greater than 56 grams 

 of iron to every 32 of oxygen, the haemoglobin phase of the reaction 

 must be almost complete and the quantities of haemochromogen and 

 haematin neghgible. 



Conant and Scott suggest, on the other hand, that while most of 

 the oxygen is present in chemical combination, an additional portion 

 is adsorbed; if so there should be more than 32 grams of oxygen 

 to 66 of iron in blood. 



