OXYGEN FIXATION IN BLOOD 587 



measurement in special application to haemoglobin and its 

 derivatives has been brilliantly developed by G. Hiifner. 21 

 "The direction of prospective improvement of method," 

 says Hiifner, "was indicated beforehand in the recording 

 of the spectral image photographically, so often done previ- 

 ously with good results. The method is particularly ad- 

 vantageous because the long-drawn photometric observa- 

 tion can be interrupted for the quickly accomplished record- 

 ing on the spot of the general spectral field, allowing, for 

 example, rapid chemical reactions which occur with a change 

 of light absorption* to be followed with ease and exactness. " 

 It is a matter of interest that the fundamental studies which 

 have led to the development of the photographic-photometric 

 method, have been applied by an astronomer (K. Schwarz- 

 schild) to the study of the stars a fine example of organic 

 exchange between two widely separated, flourishing branches 

 of the tree of modern science. 



Coefficients of Absorption, Invasion and Evasion. Con- 

 sideration of oxygen fixation in the blood must necessarily 

 be based upon the general laws of solution of gases in fluids. 

 We have therefore to deal with the coefficients of absorption, 

 invasion and evasion. The absorption coefficient is that 

 amount of gas which is contained in one cubic centimetre 

 of a fluid saturated with gas at C. and at 760 mm. pres- 

 sure. That quantity of gas which at given temperature 

 and 760 mm. pressure will penetrate into the fluid in the 

 course of one minute through a surface of one square centi- 

 metre is known as the invasion coefficient. That quantity 

 of gas which will escape in one minute from a surface of 

 one square centimetre, providing one cubic centimetre of 

 the fluid contains one cubic centimetre of gas, is spoken of 

 as its evasion coefficient. 



Oxygen is absorbed in the plasma, but is peculiarly com- 



91 Literature upon Spectrophotometry of the Haemoglobins : Burcker, Tiger- 

 stedt's Handb. d. physiol. Methodik, 2', 68, 1910. 



