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ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



area is attached a metal plate and ring, so that the membrane as a whole 

 may be lowered and raised. The upper orifice of the bell- jar is closed 

 by means of a rubber cork bearing a relatively narrow inlet tube. This 

 chamber is traversed by a horizontal tube of very soft rubber, draining 

 a receptacle filled with water. 



Allow the water to flow steadily through this tube. Then lower 

 the rubber membrane (diaphragm), thereby decreasing the pressure in 

 the glass compartment (intrathoracic pressure). Note that the "pul- 



FIG. 92. DEVICE TO ILLUSTRATE THE INFLUENCE OF THE RESPIRATORY MOVEMENTS 

 UPON THE FLOW OF THE BLOOD THROUGH THE PULMONARY BLOOD-VESSELS. (Heriug) 



A, Bell jar; B, rubber membrane closing it; V, soft-rubber pouch to imitate the pul- 

 monary blood-vessels; GH, arrangement for forcing water through V under a constant 

 pressure; j t manometer connected with "intrapleural space." On inspiration, pro- 

 duced by moving the rubber membrane downward, the intrapleural pressure is decreased. 

 This gives rise to an aspiration which tends to pull the wall of V outward, facilitating 

 the flow from G to H. 



monary blood-bed," as represented by the thin rubber tube, is now large, 

 allowing a free through flow. The opposite effect is produced by rais- 

 ing the diaphragm. The caliber of the pulmonary blood-vessels is then 

 decreased and the pulmonary resistance increased. 



5. Effect of Decreased Atmospheric Pressure. Place a mouse under 

 the bell-jar of an ordinary air-pump. Allow the pressure existing within 

 this compartment to be recorded by means of a mercury manometer 

 connected with the suction tube of the pump. Apply suction, lowering 



