APPENDIX 



THIS appendix contains a description and discussion of several special 

 methods of blood examination associated with my name, together with 

 modifications introduced by myself and others since the methods were 

 originally described. Methods of gas analysis are not included, since 

 these are collected in my book "Methods of Air -Analysis." 



Until a few years ago the gases present in the easily dissociable and 

 free state in blood were universally determined by means of the mercurial 

 vacuum pump, which had been gradually perfected by Lothar Meyer, 

 Ludwig, Pfliiger, and others, while Leonard Hill had considerably 

 simplified it for ordinary uses. It required, however, an inconveniently 

 large amount of blood and was also not very accurate, since even when 

 large volumes of blood were used errors due to gas adhering to the glass 

 could not be avoided. The presence of these errors was clearly shown by 

 the fact that the amount of nitrogen apparently obtained from the blood 

 was not only variable, but much greater than the amount which the blood 

 was capable of dissolving. The excess of nitrogen could be calculated as 

 due to contamination with air from the pump; but this correction was 

 not very satisfactory, since gas must also be left in the pump at the end 

 of the operation of pumping. The discovery which I made in 1897, that 

 oxygen or CO can be liberated quantitatively from oxyhaemoglobin or 

 CO -haemoglobin by ferricyanide, 1 made it possible to dispense with the 

 blood pump and greatly simplify blood-gas determination and increase 

 its accuracy. With the new method Lorrain Smith and I found also that 

 the oxygen capacity of blood varies exactly as its coloring power, so that 

 the oxygen capacity can be determined colorimetrically. The methods 

 now to be described are based partly on the ferricyanide reaction and 

 partly on the colorimetry of blood. 



A. Determination of Oxygen Capacity of Blood Haemoglobin 



by Ferricyanide 



The following method of determining very accurately the oxygen 

 capacity of the haemoglobin in blood or a solution of haemoglobin was 

 first fully described in ipoo. 2 Although the oxygen capacity can be de- 

 termined with much smaller quantities of blood by the apparatus de- 

 scribed below, it seems useful to describe also the earlier method, as it 



^aldane, Journ. of Physiol., XXII, p. 298, 1898. 

 2 Haldane, Journ. of Physwl., XXV, p. 295, 1900. 



