The acquisition of oxygen by the blood in the lung 213 



before the reader about the effect of temperature on the CO-0 2 - 

 haemoglobin equilibrium. 



Hartridge (6) , like Haldane and Douglas, reinvestigated the whole 

 field of accessory conditions which influence the reaction between 

 haemoglobin and carbon monoxide the eifects* of C0 2 , acids, tem- 

 perature, &c., on the equilibrium. One observation has reference to 

 the effect of temperature on micef. I give it in his own words: 

 " There are however, oddly enough, experiments on mice in the same 

 paper quoted, which do agree, the experiments being as follows: the 

 mice were placed in the cold so that their rectal temperatures fell in 

 certain cases below 19, and it was found that then the CO saturation 

 reached was higher than that obtained at normal temperature ; that 

 is to say the same effect as similar experiments performed in vitro. 

 The mere effect of temperature may therefore explain them." Per- 

 haps the most striking data which he obtained were those of the 

 influence of light on the reaction. 



This had not been overlooked by Haldane, nevertheless the 

 following figures show the need of special precautions for excluding 

 the effect of light in a very striking way. 



Percentage saturation of a haemoglobin solution with CO 

 under various circumstances of illumination. 



Dark 96 / Sunlight 40 / Dark 91 / 



Sunlight 42 / Electric light 88 / Daylight 80 / 



Sunlight 35 / Dark 92 / 6" Magnesium 64 / 



Of these the most interesting is, I think, the daylight. When one 

 considers that the method of carmine titration deals with solutions of 

 only one-tenth of the concentration of that used by Hartridge and 

 for that reason much more accessible throughout its whole mass to 

 the active (ultra violet) rays, one will see that there is at least the 

 possibility of grave errors entering into the carmine method unless 

 special precautions are taken which are defined by quantitative 

 estimations, and if it is necessary to define such a source of error in 

 units in the notoriously gloomy atmosphere of these islands, it is 

 much more necessary to do so in the intensely actinic atmospheric 

 conditions which obtain at higher altitudes and lower latitudes than 

 our own. 



* The same results were arrived at independently by Haldane, Haldane and 

 Douglas, Journal of Physiol. XLIV, p. 303, 1912. 



t These experiments are quoted on p. 187 and tabulated on p. 188 of this volume. 



