THE OXYGEN IN BLOOD 



531 



is about 4-9 per cent. (^-.5) of the body-weight and varied in the 

 fourteen persons examined between 3-34 per cent. (^) and 6'27 

 per cent. (^g-). The total oxygen capacity of the blood in litres 

 is about O85 per cent, of the body- weight in kilograms, and 

 varied between 0-57 per cent, and 0-95 per cent. The total oxygen 

 capacity is, relatively to the body-weight, more constant than the 

 mass of the blood. 



Sufficient data have now been given to show that the oxygen 

 capacity of the blood depends upon the colouring matter of the 

 red corpuscles, but it remains to discuss why solutions of crystal- 

 lised haemoglobin do not behave in the same manner as blood, 

 why they have different oxygen capacities. There seems to be 

 little doubt that the pigment of the red corpuscles is not the same 

 as crystallised haemoglobin ; the corpuscles contain about 40 per 

 cent, of hemoglobin, but it is impossible to make such a strong 

 solution with crystals of haemoglobin. Bohr maintains that there 

 are at least four different kinds of haemoglobin, which combine 

 with different amounts of oxygen and have different " specific 

 oxygen capacities," by which term he designates the ratio between 

 the number of grm. of iron and the number of cubic centi- 

 metres of oxygen present in a given volume of blood, blood- 

 corpuscles, or solutions of haemoglobin saturated with air at 

 ordinary pressure and temperature. The red corpuscles are said 



