520 OXYGEN CONTENT OF BLOOD IN PNEUMONIC INFLUENZA, 



the measurement were avoided. The electromotive force of a 

 cell made up of a hydrogen electrode dipping into this plasma 

 and a decinormal calomel electrode was then measured as de- 

 scribed by Michaelis (1911) . The plasma was connected with 

 the calomel electrode by means of a siphon containing saturated 

 ammonium nitrate. A capillary electrometer was used as the 

 null instrument; the readings were made on a Wolff's poten- 

 tiometer to the nearest millivolt. The acidity or concentration 

 of hydrogen ions (C H ) is calculated from the observed electro- 

 motive force by the equation : 



log ^= pH = (E— 0.337) A- 

 where E is the observed E.M.F., and k a factor which varies 

 slightly with the temperature. 



The reactivity of the plasma towards acid may be determined 

 in two ways: (1) by measuring the amount of acid required to 

 alter the reaction by an arbitrary extent, or (2) by measuring 

 the change of reaction produced by an arbitrary amount of acid. 

 In practice the latter method is much the simpler and more 

 convenient. Cullen (loc. cit.) showed that it was convenient to 

 add an amount of acid sufficient to liberate all the combined 

 carbon dioxide in the plasma, the liberated gas being got rid 

 of by exposure to a reduced pressure, as described above. In 

 the present work, the change of acidity produced by adding 2 

 volumes of 0.0196N HC1 was mej ed after pumping off ihe 

 liberated carbon dioxide. 



In the following table are shown the oxygen content and 

 capacity of a number of samples of venous blood from cases of 

 pneumonic influenza. The percentages of haemoglobin as deter- 

 mined colorimetrically in the von Fleischl hamioglobinometer, 

 and as calculated from the oxygen capacity, are also shown. 



