50 Chapter IV 



highly probable that it depends upon the method employed. The 

 following are the data of the curves obtained for man and the dog : 



Blood at approximately 40 mm., tension of C0 2 and 37 39 C. 



Abscissa 10 15 20 25 30 35 40 45 50 60 80 100 160 mm. 2 



21 ' 5 45 ' 5 59 ' 5 69 75 ' 5 80 83 ' 5 86 88 ' 5 91 ' 5 93 ' 5 97 / 

 7 11-5 18 ' 5 20 ' 5 32 ' 5 41 ' 5 50 ' 5 60 ' 5 69 80 88 ' 5 90 ~/ 



It is scarcely possible to leave the subject of the action of salts 

 upon haemoglobin without saying what there is to be said on this 

 question of how they act. 



This has to some extent been foreshadowed in the previous 

 chapter. The theory which we wish to discuss is that, while the 

 actual union of the oxygen and the haemoglobin is a chemical action, 

 the quantity and character of the salts present cause the molecules 

 of haemoglobin to adhere to each other in varying degrees. Any 

 alteration in the degree of aggregation of the molecules would by the 

 laws of mass action entail an alteration in the dissociation curve. 



First of all let us discuss the question of whether there is any 

 independent reason for supposing that the presence of salts does 

 produce such an aggregation of the molecules. 



The evidence on this head is two-fold : 



(1) Roaf showed that the osmotic pressure of haemoglobin in the 

 presence of salts, i.e. in blood laked with water or with very dilute 

 sodium bicarbonate, corresponded to aggregates of about two mole- 

 cules. Hiifner and Gansser with pure haemoglobin obtained results 

 corresponding to one molecule. 



(2) Mines has shown that a dialysed solution of haemoglobin is 

 precipitated by minute quantities of trivaleht ions in just the same 

 way as it is by acids, and precipitation is only one stage further than 

 aggregation. 



The colloidal nature of haemoglobin*. 



Although it is certain that the union between haemoglobin and 

 oxygen is a true chemical combination and not a mere surface ad- 

 sorption, the colloidal condition of haemoglobin remains of great 

 importance as a factor influencing the equilibrium between haemo- 

 globin and oxygen at relatively low oxygen tensions. For although 

 the oxygen capacity of haemoglobin must be independent of the state 

 * I am indebted to Mr Mines for the following note. 



