CHAPTER XIII 



THE ACQUISITION OF OXYGEN BY THE BLOOD IN THE LUNG 



(CONTINUED) 



No apology is put forward for the point at which I have drawn 

 the dividing line between the present and the last chapter. It has 

 been drawn at the position in which the subject stood when Hartridge 

 commenced his work. The purely personal point of view from which 

 this volume has been written demands the treatment of the subjects 

 in a personal w r ay. But for Hartridge's work and a trifling contribu- 

 tion made by Cooke and myself the subject of pulmonary secretion 

 would probably have found no place in the book. The last chapter 

 then forms a statement of the problem as it appeared when Hartridge 

 commenced to work at it. 



Whilst he was working, two researches of great importance ap- 

 peared, which quite altered the aspect of the problem. The first was 

 the work of Dr and Mrs Krogh (1) , the second the work of Haldane 

 and Douglas 12 '. The first clearly proved that in animals under opera- 

 tion all the facts involved in the acquisition of oxygen could be 

 explained by diffusion. The second consisted in a withdrawal of the 

 secretory theory except during conditions of stress, i.e. either of 

 considerable exercise in which the demand for oxygen w r as greatly 

 increased or of reduced barometric pressure under w r hich the supply 

 is diminished. 



It will be desirable to treat of these two researches in some 

 detail. 



The change which has taken place within the last three years has 

 largely been caused by an altered point of view with regard to the 

 requirements and possibilities of gas analysis as adapted to physiologi- 

 cal purposes. The generation w r hose hairs are grey in general held to 

 a sound chemical principle, namely that the greater the quantity of the 

 substance which could be obtained for analysis the more certain the 



