674 PRINCIPLES OF GENERAL PHYSIOLOGY 



named. Fig. 226 is a reproduction of a simultaneous tracing of intra-ventricular 



FIG. 226. 



PRESSURE CURVES FROM AORTA (UPPER TRACING) AND LEFT VENTRICLE 

 (LOWER TRACING). To be read from right to left. 



Note that the aortic pressure does not begin to rise until the intra-ventricular pressure has risen to the level of S\. 



The wave at S\ on the ventricular curve lies in time between K and 8-2 of'the aortic curve. 



The notch J of the aortic curve is considerably later than the beginning (IF) of the fall of pressure in the ventricle. 



(Piper.) 

 and aortic pressures, and Fig. 227 a diagram showing the relations between 



Aorta 



.Left \ 

 ventricle ) 



Left | 

 auricle ) 



FIG. 227. CURVES SHOWING SIMULTANEOUS CHANCES OF PRESSURE 

 IN THE AORTA, LEFT VENTRICLE, AND LEFT AURICLE, IN 

 ORDER FROM ABOVE DOWN. To be read from left to right. 



1, Systole of auricle. 



a, Closure of auricula-ventricular valve. 

 6, Opening of aortic valve. 



3, Sudden fall of intra-ventricular pressure. 



c, Closure of aortic valve. 



4, Slow rise of pressure in auricle, due to inflow of blood from the veins. This 



pressure falls again as soon as the relaxed ventricle allows blood to enter it. 



the pressures in left auricle, left ventricle, and aorta. 



(After Piper.) 

 The chief points to be noted 



