130 



PEACTICAL PHYSIOLOGY 



key, and are placed in position under the peripheral end of the vagus 

 nerve. The clip is then removed from the carotid artery and the 

 kymograph started. Note the height of the arterial pressure, the 

 cardiac pulsations, and the respiratory oscillations of arterial pressure. 

 The pulsations are distorted by the momentum of the mercury. 



BAIRD&TATLOCK4.0NEON 



FIG. 107. Bering's apparatus for demonstrating the action of the respiratory pump. 

 A, Glass bell, thorax ; B, air-tight base ; K, diaphragm ; C, trachea leading to lungs ; I, 

 manometer ; E, tube opening into A ; F, heart with valves V. The action of the diaphragm 

 pumps air in and out of the lungs and water through the heart. The kings and heart are 

 thin rubber bags. 



The arterial pressure, if the respiration is slow, begins to rise during 

 the second third of inspiration, and begins to fall during the second 

 third of expiration. If the respiration is rapid the pressure rises 

 during expiration and falls during inspiration. The inspiratory fall 

 of intra-thoracic pressure aspirates blood into the intra-thoracic veins 

 and thin walled auricles, and dilates the pulmonary vessels. The descent 

 of the diaphragm expresses blood from the liver and abdominal vessels 

 into the right heart. Expiration has the opposite effect in each respect. 



When the respiration is rapid the inspiratory dilatation of the 



