242 Chapter XVI 



borne in mind that it is more important that the blood should become 

 more rapidly reduced in the active tissue than more rapidly oxidised 

 in the lung of the active person. This is most evident if a very small 

 muscle be considered. Let it be in full activity: the blood will go 

 through it with ten-fold rapidity, hence the necessity for rapid reduc- 

 tion of the haemoglobin : but the muscle being small the quantity of 

 blood involved would not be so large as greatly to quicken the circu- 

 lation through the lung the blood would have its usual time for the 

 acquisition of oxygen. 



It seems impossible to close this chapter without some reference 

 to the controversy as to the exact nature of the chemical stimulus to 

 the respiratory centre. 



Haldane and Priestley (1) , some ten years ago, made a great advance 

 in the physiology of respiration by demonstrating in the most con- 

 vincing manner that the respiratory centre was normally stimulated 

 by carbonic acid. Since the issue of their paper there have been two 

 views held by physiologists as to the status of carbonic acid as 

 a stimulus. One school, including Laqueur and Verzar (2) , hold that 

 C0 2 is a specific stimulant and that other acids would not have the 

 same effect : others, of whom Winterstein has been one of the most 

 outstanding, have held the view put forward by Haldane and 

 Boycott that C0 2 merely acts because it is an acid and that any 

 other acid would do as well. The climbs at Carlingford seem decisive 

 on this point; in them we have the C0 2 concentration decreasing 

 while, as Haldane and Boycott (3) predicted, the total hydrogen ion (4) 

 concentration increases. The stimulus to the respiratory centre 

 cannot be simply the C0 2 , for were it so the breathing would be 

 slower rather than faster. 



REFERENCES 



(1) Journal of Physiology, xxxn, p. 225, 1905. 



(2) Laqueur and Verzar, Arch.f. d. ges. Physiol. CXLIII, p. 395, 1911. 



(3) Haldaue and Boycott, Journal of Physiology, xxxvn, p. 355, 1908. 



(4) Appendix IV. 



