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THE ROYAL SOCIETY OF CANADA 



The results grouped under "I" show a decrease and those under 

 "11" show an increase in breathing. Considering first of all the 

 experiments of Group II it will be observed that the oxygen saturation 

 of the blood runs in the same direction as the change in breathing and 

 that the percentage of oxygen in the alveolar air increases as the 

 breathing increases. These results indicate that although relative 

 deficiency of oxygen in the blood, and presumably, therefore, a de- 

 creased tension of ox^^gen in the plasma, may be directly responsible 

 for the stimulation of respiration at the beginning of anoxaemia 

 (cf. Table I) such cannot be the cause of the still greater stimulation 

 which developes later. Since, as our results show, the blood becomes 

 more, and not less saturated with oxygen as the anoxaemia progresses, 

 we must conclude that some other respiratory stimulant has made its 

 appearance and the question arises as to its nature. The gradual 

 development of the hyperpnoea during the anoxaemia suggests that 



