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A TEXTBOOK OF PHYSIOLOGY 



monary artery, relaxation of the ventricular walls, opening of the 

 auriculo- ventricular valves so as to allow the passage of blood from 



o 



auricle to ventricle, and diminished pressure of apex against chest 

 wall. During the long pause there are taking place (1) gradual re- 

 filling of the ventricle from the auricle; (2) contraction of the auricle 



