530 



THE RESPIRATORY EXCHANGE 



Comparative determinations of the oxygen capacity of blood 

 have been made by Haldane with the ferricyanide method and the 

 blood-pump ; the results for the two methods are practically the 

 same, as shown by the following table. 



There is very little doubt that, apart from the small quantity 

 of oxygen in simple solution, the whole of the oxygen which can 

 be extracted from blood is in combination with the haemoglobin. 

 It is, therefore, of interest to determine whether the oxygen capa- 

 city of the blood varies with the colouring power. Haldane and 

 Lorrain Smith ( ls ) have produced satisfactory evidence that this is 

 the case for different samples of blood taken not only from the 

 same individual, but also from different animals. The oxygen 

 capacity of any blood can thus be determined by comparing it 

 colorimetrically with a sample of blood, the oxygen capacity of 

 which has been determined by the ferricyanide method or the gas- 

 pump. In this way Haldane has been able to give an exact value 

 to clinical estimations of haemoglobin ; a 1 per cent, solution of 

 ox or sheep's blood of 18' 5 per cent, oxygen capacity is used as 

 a standard solution for the hsemoglobinometer. The following 

 (see p. 531) are the results of some of his observations upon 

 the blood of healthy men, women, and children. 



The average oxygen capacity of the blood in healthy adult 

 men was 18-5, in women 16*5, and in children 16' 1 per cent. 



It is necessary to know not only the percentage but also the 

 total oxygen capacity of the blood. Haldane and Lorrain Smith 

 determined these in their research on the mass and oxygen 

 capacity of the blood in man. The mass of the blood in man 



