506 THE OUTGO OF ENERGY 



slightly. Raise the water level slowly till the 

 lung is slightly but evenly distended. 



Note the pressure in the pleural cavity. Is it 

 positive or negative ? Why ? 



Normal Respiration. Slowly and rhythmi- 

 cally raise and lower the diaphragm (water level) 

 between the inspiratory and expiratory level, 

 taking care that the lung never becomes even 

 slightly collapsed a.t the end of expiration. 



Give reasons for the changes in the intra- 

 pulmonary pressure. 



Forced Respiration. Eaise and lower the 

 diaphragm more quickly. 



Observe that the differences in pressure are 

 increased. 



Obstructed Air Passages. Diminish the inlet 

 in the respiratory tube by moving the glass plug. 

 Raise and lower the diaphragm. 



The differences of pressure will be increased. 



Asphyxia. Close the entrance to the lungs 

 entirely. 



Note the effect of movements of the diaphragm 

 upon the intra-thoracic and intra-pulmonary 

 pressures. 



Coughing: Sneezing. Remove the glass rod 

 from the respiratory passage. Bring the lung to 

 full inspiration. Close the respiratory opening 

 with the moistened thumb. Raise the diaphragm 



