118 



RESPIRATION 



that artificial inflation of the lung (Positive Ventilation) 

 caused cessation of breathing; standstill occvirring in the 

 expiratory position. Suction of air out of the lung, on 



Positive ventilation. 



Diuplirai-'ni. 

 I Seconds. 

 Fig. 25. — -Positive ventilation. 



Ainspiration. 

 4' Expiration. 



the other hand (Negative Ventilation), is followed by 

 cessation, but in the opposite phase; standstill now 

 occurring in inspiration. These effects were found to be 

 conditional upon the integrity of the vagi. 



Negative ventilation. 



at) 01 



Diaphragm, 



Alnspir; 

 ^-Expiratioi 



SeconUtJ. 



Fig. 26. — -Necrative ventilation. 



The results show that on distension of the lung an impulse 

 travels up the vagus which stimulates the medulla to 

 produce relaxation of the diaphragm, while relaxation of 

 the lung tissue, on the other hand, causes contraction of 

 the diaphragm. 



Head then proceeded to stimulate the vagus. Using 

 the rabbit, where the nerve is free from depressor fibres, 



