32 THE NEW PHYSIOLOGY. 



their previous actual distribution, of which no account 

 is given. 



Now let us try to analyse an actual example of 

 physiological investigation. I have sometimes been 

 good-naturedly chaffed by physiological brethren for 

 preaching anti-mechanistic doctrines, and actually em- 

 ploying rigid physical and chemical methods in experi- 

 mental work, and reaching equally definite physico- 

 chemical results ; so I will select for analysis the corner 

 of physiology at which I have mainly worked, namely, 

 the physiology of respiration. 1 



The act of breathing consists of rhythmic muscular 

 movements of the chest-walls, causing the lungs to 

 expand and contract, and air to enter and leave them. 

 These movements of the air are accompanied by chemical 

 changes, oxygen being absorbed from it in the lungs, 

 and carbon dioxide being given off. This is a general 

 statement in physical and chemical terms of the most 

 evident phenomena connected with respiration, and we 

 have now to follow up the physico-chemical analysis. 

 The oxygen which disappears in the lungs passes into 

 the blood through the very delicate epithelium lining 

 the walls of the lung alveoli ; and during rest under 

 ordinary physiological conditions the passage inwards 

 has been found to occur in strict accordance with the 

 known laws of physical diffusion of gases. Nearly all 

 of this oxygen then enters into a loose and easily dis- 

 sociable chemical compound with the haemoglobin con- 

 tained in the red blood-corpuscles of the venous blood 



1 The papers published by my pupils and myself on this sub- 

 ject will be mostly found in the Journal of Physiology from 1892 

 onwards. 



