n8 



RESPIRATION 



gen to the inspired air the periodicity disappears. This experiment 

 was carried out repeatedly by Douglas, Yandell Henderson, 

 Schneider, and myself, on Pike's Peak, and never failed. 9 Mosso 

 had attempted to carry it out, but got a negative result owing to a 

 defective mode of administering the oxygen. 



As already seen periodic breathing can easily be produced at 

 ordinary barometric pressure by suitable means. As the barometric 

 pressure is reduced the periodic breathing is produced more and 

 more readily, and is more and more persistent, just as might be 

 expected; and the same is true if, instead of a reduction of bar- 

 ometric pressure, there is a reduction in the oxygen percentage of 

 the inspired air. This form of periodic breathing has no pathologi- 

 cal significance, and occurs during perfect health. 



The special characters of the increased breathing caused by 



Figure 39. 



(a) Rebreathing Concertina filled with oxygen CO* accumulating, 



(b) Rebreathing Concertina filled with air CO 2 accumulating. 

 Time-marker = 2 seconds. Arrow shows point where lips were distinctly blue. 



anoxaemia were recently studied by Meakins, Priestley, and 

 myself. 10 The differences between increased breathing caused by 

 excess of CO 2 and that caused by anoxaemia, or by anoxaemia 

 accompanied by excess of CO 2 , are very striking. Speaking gen- 

 erally, the effect of excess of CO 2 is mainly to increase the depth 

 of breathing, and only a moderate increase of frequency is pro- 

 duced. On the other hand anoxaemia produces a marked increase 

 in frequency and only a moderate increase in depth. But when the 



* Douglas, Haldane, Yandell Henderson, and Schneider, Philos. Trans. Royal 

 Society, B. 203, p. 231. 



"Meakins, Haldane, and Priestley, Journ. of Physiol., LII, p. 420, 1919. 



