ABSTRACT
Measurements of the oxygen content of blood have been carried out for many years using a variety of methods many of which may be described as volumetric methods, e.g. Van Slyke and Natelson. In recent years methods applicable to small samples (10–20 μl blood) have been developed especially in relation to studies of comparative physiology. Volumetric methods depend upon the release of oxygen chemically bound with haemoglobin, which is frequently achieved by treatment with ferricyanide. With the release of oxygen the resulting increase in 
can be measured. If the volume is known then the quantity of oxygen released can be estimated. Methods using this principle have been developed by a number of authors including Fabel & Liibbers (1964) and a method using a small cuvette has been described by Tucker (1967).
