UNION OF HAEMOGLOBIN AND OXYGEN 251 



atmospheric pressure (160 mm. Hg.) each litre of blood will take 

 up 200 c.c. of oxygen. Leaving out of account the relatively 

 small amounts of oxygen carried in solution in the plasma and 

 adsorbed by the plasma proteins, we may calculate that each 

 corpuscle will carry oxygen to the extent of 



Total oxygen capacity of blood 1000 



J = 4 XlO" 11 c.c. 



Total number of corpuscles 25 xlO 12 



Each cubic centimetre of oxygen will need 25 Xl0 corpuscles 

 to carry it. 



Further, the total iron content of human blood is about 2-5 

 grams (Schmidt). 



That is, each gram of iron is associated with 1000/2-5=400 c.c. 

 of oxygen a figure closely approximating to Barcroft's experi- 

 mental finding of 401 c.c. Normal blood contains 14 grams per 

 cent, of haemoglobin. It follows that each corpuscle carries 



140 x5 



=28 xlO- 12 grams of haemoglobin. In other words, each 

 25 X 10 12 



cubic centimetre of oxygen postulates the presence of 



28X25 XlO 9 



=0-7 gram, of Hb. 



10 12 

 The iron content of Hb. must therefore be - - gram 



/ 



per gram of Hb. Putting this in molecular terms, one molecular 

 proportion of iron (56 grams) enters into the composition of 

 15,680 grams of Hb. The molecular weight generally given for 

 Hb is 16,660. 



Evidence has been produced which shows that when haemo- 

 globin is fully saturated with oxygen there are 401 c.c. of oxygen 

 for every gram of iron. That is, each combining proportion 

 of iron (56 grams) co-exists with two combining proportions 

 (32 grams) .of oxygen. From this, some deduce the presence of a 

 compound FeO 2 in haemoglobin. That may be. On the other 

 hand, the idea of a chemical combination between haemoglobin 

 and oxygen raises hosts of difficulties which would not arise on 

 the hypothesis of adsorption of gas on a colloidal surface. How- 

 ever, no reliable direct experimental evidence bearing on this has 

 come to hand. If analogies could be taken as a proof instead 

 of analysis, the adsorption theory would hold the field un- 

 disputed. 



