568 



THE RESPIRATORY EXCHANGE 



better, and the respirations were continuous, the percentage com- 

 position of his alveolar air was 4-44 volumes of carbon dioxide 

 and 16-34 volumes of oxygen. Observations showed that a 

 diminished as well as an increased supply of oxygen would abolish 

 the period of apncea, and by the inhalation of carbon dioxide 

 in percentages varying from O76 to 11- 33 all gradations from 

 feeble respirations in the place of apnoea to continuous breathing 

 of almost regular type could be obtained. Doses of carbon dioxide 

 above 1 per cent, readily abolished apnoea, and large doses could 

 be tolerated more readily by the patient than by normal subjects. 

 A suitable mixture of carbon dioxide and oxygen produced a 

 regular and easy respiration. 



It would appear that the periodicity of Cheyne-Stokes's respira- 



FiG. 33. Cheyne-Stokes's Respiration in Man (Pcmbrey and Allen). 

 The curve reads from left to right, and the time is marked in seconds. 



tion is due to a diminished excitability of the nervous system 

 and defective circulation ; the carbon dioxide accumulates and 

 the oxygen diminishes, until at last the nerve-cells of the respiratory 

 centre are stimulated, the waxing respirations begin and culminate 

 in marked dyspnoea, whereby the carbon dioxide is washed out 

 and a large quantity of oxygen is taken in ; apncea follows, due 

 apparently to the absence of sufficient carbon dioxide to stimulate 

 the nerve-cells. The alteration in the excitability of the nerve- 

 cells may or may not be necessary in addition to defective circu- 

 lation, indeed it may be caused by the latter. The occurrence 

 of Cheyne-Stokes's respiration as a normal event in the respiration 

 of hibernating mammals, in infants, and in some healthy adults 

 during sleep, and as a characteristic of some cases of poisoning, 

 is a subject of further investigation from these points of view. 



