FLOW OF BLOOD THROUGH THE ARTERIES 1041 



goes on uninterruptedly, but in the aorta there is a sharp elevation 

 immediately after D. This elevation is the dicrotic wave. We thus see 

 that it comes immediately after closure of the aortic valves. 



AB 



CD 



CD 



AB 



Sec. 



0.7 



Diastole 



FIG. 410. Diagram (after HURTHLE) showing simultaneous cardiographic, 



endocardiac, and aortic curves. 



I, cardiogram ; II, endocardiac pressure ; in, aortic pressure ; iv, aortic 

 pressure, corresponding to dotted endocardiac curve in n. 



There are several factors at work tending to produce a secondary 

 wave at this point. With the sudden cessation of the inflow of blood 

 from, the ventricles at the end of the ventricular contraction a negative 

 wave must be produced at the beginning of the aorta, which, trans- 

 mitted along the arterial system, will tend to produce a reflux of blood 

 towards the heart. The movement so caused is reinforced by the elastic 

 .reaction of the arterial wall so that the returning blood is driven up 



66 



