TECHNIC OF BLOOD GAS ANALYSIS 585 



by means of blood gastonometers 17 as used by Pfliiger, Fred- 

 ericq, Bohr, Krogh and Lowy. They all depend on the prin- 

 ciple that blood is brought in contact with a mixture of 

 gases until a complete tension balance is attained and the 

 partial pressure of the gases is then determined. The 

 balance is quickly obtained if the volume of gas is reduced 

 to a minimum as in a microtonometer. 



In the method of Haldane and Lorraine Smith the oxygen 

 is determined in a specimen of blood by means of ferri- 

 cyanide ; in another specimen the oxygen is forced out by 

 carbon monoxide and the color of the carbon oxide blood 

 compared with a carmine solution of known proportions. 

 Plesch has proposed a wedge haemoglobinometer ; the blood 

 to be tested, diluted 200 times, is converted into carbon- 

 oxide blood by shaking it up with illuminating gas and this 

 compared with a standard fluid (blood with known propor- 

 tion of carbon oxide) . The apparatus consists of two gradu- 

 ated tubes, one of which receives the blood to be tested, the 

 other the standard fluid. In the latter is a wedge arranged 

 so that the visual thickness diminishes from below upwards. 

 The result is read off by observing the tubes through a 

 small aperture and moving one tube until the colors coin- 

 cide. In a method devised by Zuntz and Plesch, which has 

 been found applicable to the study of circulating blood in 

 the living animal, the carbon oxide is forced out of the blood 

 by potassium ferricyanide, oxidized into carbonic acid by 

 passing over glowing platinum, the carbonic acid absorbed 

 by potassium hydrate and the carbon oxide determined by 

 Barer of t-Haldane method from the observed change of pres- 

 sure. Dreser has also devised a method for determining 

 the carbon oxide combined in small quantities of blood ; in 

 which he uses a small mercury pump, measuring the amount 

 of gas obtained in a capillary tube. 



The new nitrous oxide method devised by Zuntz in col- 

 laboration with Markoff and Franz Miiller provides a very 



17 Cf. Literature in Ch. Bohr, Skandin. Arch. f. Physiol., 17, 205, 1905. 



