26 



RESPIRATION 



could affect the respiratory center. In Figure 6 the distention wa^ 

 sufficiently prolonged for the "apnoeic" blood to affect the center 

 before the end of distention. The effect is therefore similar to 

 that in Figure 2. 



v^wwn 



^A/'vvvvw^ 



Figure 4. 



finrr«i»«»'''»nf«»»**»»i»»' n i m nr>»'>vi»» i> »» '»<<»» > » irt'» »vt» »>»>?« t» 



.j,^ 



^'^aaAaAAA/ 



Figure 5. 



Tn n »»»f >» r *»'ri 



»»»ni<i>r»<«»wr»'f w i n »»t>«» f <i rr» rr*'i » 



4^r 



Figure 6. 



Effects of distention with pure air for increasing short 

 periods. Crosses show beginning and end of distention. To read 

 from left to right. Fig. 4 distention for i sec. ; Fig. 5 for 3 sees. ; 

 and Fig. 6 for 5 sees. 



The regularity of ordinary breathing is constantly being inter- 

 fered with in various ways, as for instance during talking or 

 singing; and the breath can if necessary be held for about a minute 

 by voluntary effort. The readiness with which these interruptions 

 occur has given rise to the popular idea that the supply of air to 

 the lungs is to a large extent under voluntary control, and can be 

 increased or diminished by proper training. In reality the mean |^ 

 ventilation of the lungs is not affected by ordinary interruptions. 



