THE MECHANISM OF RESPIRATION 



279 





Upper curve shows lung volume, lower arterial pressure of cat with right vagus cut. 

 At indication mark 0-0075 gramme of pilocarpine nitrate injected. There is 

 constriction of the bronchial muscles, which diminishes the amount of air entering 

 and leaving the lungs. The blood-pressure falls. Both effects are due to stimu- 

 lation of the vagus nerve-endings. (Brodie and Dixon.) 



FIG. 148. 



Upper curve represents the volume of small lobe of lung, amount of air entering and 

 leaving lung shown respectively by up-and-down strokes. Lower curve, blood- 

 pressure. At indicated marks two small doses of lobelia injected into a vein. 

 There is almost immediate dilatation of the bronchioles; the rise in blood -pressure 

 is a vaso-motor effect. (Brodie and Dixon.) 



resting man, 300 to 500 c.c. The amount of air which can be taken 

 into the lungs by forced inspiration after a normal quiet inspiration 

 is the complemental air, averaging 1,500 to 2,000 c.c.; that which 

 can by forced effort be expelled from the lung after a quiet expiration 



