fHE CONTROL OF THE RESPIRATION 385 



C0 2 in the air each time, the length of the apneic pause proportionally 

 increases as the C0 2 pressure in the inspired air diminishes. 



Periodic Breathing 



TYPES OF PERIODIC BREATHING 



In the best known of these, called Cheyne-Stokes respiration, a period 

 of hyperpnea supervenes upon one of apnea, each period following in 

 regular sequence. After an apneic period, the breathing begins at first 



Fig. 132. Various types of periodic breathing. (From Mosso's "Life of Man in the High Alps.") 



faintly, gradually becomes more pronounced until it is markedly exag- 

 gerated, and then fades off again to the apneic pause. Sometimes the 

 apneic period is immediately followed by one of intense hyperpnea, there 

 being no gradual increase in the respiratory movements. Between these 

 two types all varieties of the condition are met (Fig. 132). 



The conditions in which periodic breathing occurs may be divided into 



