The acquisition of oxygen by the blood in the lung 215 



Percentage saturation with CO in blood exposed to alveolar air. 



Series 3. Worl: 



(1) (2) (3) (4) (5) (6) Mean 



A In vivo 30 24 24 26 27 25 



B In vitro 28 23 20 24 23 25 



A/B 1-Ofi 1-04 1-2 1-08 1-24 1-00 1-10 



If then we regard the work of Hartridge as that in which the 

 possible errors have been most clearly defined quantitatively, and 

 accept it as being the most mature expression of opinion at the time 

 of our writing, our verdict must be that there is no evidence of 

 oxygen secretion in man as represented by a single individual 

 Hartridge either (a) at rest, or (b) under such restricted conditions 

 of oxygen want as may be induced by diminished oxygen pressure for 

 short periods of time, or (c) during moderate exercise of 4 minutes 

 duration. 



For what it is worth my own view on the question of oxygen 

 secretion at the present time is this : It is agreed on all hands 

 that there is no oxygen secretion in the resting individual. The 

 issue then may be stated thus. Is the lung capable of oxygen 

 secretion? It is alleged to be so during oxygen want, i.e. during 

 exercise, or at high altitudes or with insufficient functional haemo- 

 globin (as during partial CO-poisoning). The real point to my mind 

 is that of exercise, for it is from its advantage during exercise that 

 such a function in the lung would naturally have been evolved and 

 maintained. Exercise then is the prima facie test case here the ex- 

 periments of Hartridge and of the Oxford School disagree. Hartridge 

 finds a pressure of oxygen in the blood which is below that in the 

 alveolar air, Haldane and Douglas find the reverse. Yet their methods 

 are similar, the differences consisting in (1) the method of estimation 

 of the CO-haemoglobin in the blood and (2) the nature and duration 

 of the exercise. The issue refines itself largely into the question of 

 which of these methods is the more correct. Reading the accounts 

 of the two methods, I never fail to be greatly influenced by the follow- 

 ing facts: (1) Hartridge has tested his so exhaustively against a 

 purely objective one that of the pump. (2) He found, when 

 testing his apparatus against the pump, the method of actual 

 mixtures unreliable and had to replace it by that of optical 

 mixtures. (3) The carmine method has never been tested in any 

 other way than by that of actual mixtures. (4) Of the rival 

 workers Hartridge has tabulated his errors the more exhaustively. 



