THE PUMPING ACTION OP THE HEART 



159 



cycle. The vibrations from the two ventricles are alike, but differ from 

 those taken from the aorta. The first ventricular sound consists of from 

 five to thirteen irregular vibrations, usually in three groups, the first 

 composed of two small vibrations, the middle one of several large vibra- 

 tions, and the third of a varying number of small vibrations. The 



I II II 



A. 





.rv.r 



Wft 





B, 



c. 



Fig. 38. Electrophonograms along with intraventricular pressure curves from three dif- 

 ferent experiments. In A the uppermost curve shows the pressure, the middle one the sounds 

 of the right ventricle, and the lowermost one ihose of the aorta. P indicates the relative posi- 

 tion of the curves. M is due to mechanical oscillations. Sz indicates the second sound, and 

 /, 2, 3, and 4 the corrected time relations of the first sounds. In B, the pressure and sound 

 curves are both from the left ventricle (letters same as in A). In C, the aortic and pulmonary 

 arterial sounds are shown (letters same as in A). (From Wiggers and Dean.) 



duration of the sound is from 0.05 to 0.152 seconds, and the periodicity 

 from 0.004 to 0.054 per second. When compared with an intraventricu- 



