390 



PEACTICAL PHYSIOLOGY 



with the chamber of the pump, and the other side with the artery close 

 to the valve. Take a record, and observe how the instrument records 

 the moment when the valve opens and shuts. If a time tracing be 



rmwmmtmtm 



A/VWWI/\^ 



FIG. 251. Aortic and ventricular pressure curves taken by Hiirthle manometers. (Hiirthle.) 



taken, the time relations of the pump (ventricular contraction) can be 

 exactly determined. The period of ventricular systole is divided into 

 three : (1) the period of rising tension, when all the valves are closed ; 



EF 



FIG 252. Schema to show the velocity and resistance heads. B, Pressure bottle. A, Tube 

 with piezometers. E F, Pitot tubes. 



(2) the period of output ; (3) the period of relaxation. In simultaneous 

 records of intra-ventricular pressure and aortic pressure the beginning 

 of the aortic rise (2) marks the opening of the aortic valve and 

 beginning of output. The end of output occurs when the semilunar 



