712 PHYSIOLOGY OF RESPIRATION. 



By examination of the expired air Pembrey* has shown 

 that during the dyspneic phase the percentage of CO 2 in the 

 alveolar air is markedly diminished (2 per cent.), and he believes, 

 therefore, that the following phase of apnea is due entirely tc 

 this washing out of the CO 2 , that is, to the removal of the normal 

 stimulus to the respiratory center. Practically he finds that 

 the apneic phase can be removed by the administration of 

 either pure oxygen or carbon dioxid (2.2 to 11.2 per cent.). 

 Pembrey does not give the clinical histories of his patients, but 

 apparently he has studied cases belonging chiefly to Eyster's 

 first group. None of the suggestions made at present seem to 

 account adequately for the very labored breathing at the acme 

 of the dyspneic phase, and the phenomenon evidently requires 

 further experimental study. 



More or less rhythmical variations in the strength of the 

 breathing movements have been described also in normal sleep, 

 hibernation, chloral narcosis, high altitudes etc., but nothing so 

 definite and characteristic as in these very interesting Cheyne- 

 Stokes cases. 



* Pembrey, "Journal of Pathology and Bacteriology," 12, 258, 1908. 



