INSPIRATION 505 



XL MECHANICS OF EESPIRATION 



Artificial Scheme. Eaise the left glass rod 

 above the opening in the rubber tubing (Fig. 67). 

 Hold the lower end of the free cylinder even with 

 the rubber balloon, and pour in water till the 

 level just reaches the balloon. Lower the left 

 glass rod to cover the opening. 



The surface of the water in the attached 

 cylinder represents the diaphragm and movable 

 chest-walls; the interior of ,the cylinder above 

 the water, the thoracic cavity; and the rubber 

 balloon, the lungs. The left manometer shows 

 the in tra- thoracic pressure ; the right manometer 

 shows the intra-pulmonary pressure. The left 

 glass rod closes the entrance to the cylinder, 

 i. e. makes the thoracic cavity a closed cavity, 

 as is normal ; the right glass rod, with its lower 

 end partly covering the opening in the rubber 

 tubing, controls the entrance to the balloon (the 

 respiratory passages). 



Inspiration. Nearly close the respiratory pas- 

 sage. Lower the water level to the base of the 

 thoracic cylinder. 



Note the change in the size of the lung, and 

 in the pressure in the lung and in the thorax. 

 Give reasons for these changes. 



Expiration. Widen the respiratory passage 



