THE CIRCULATION OF THE BLOOD 



685 



tends to close again, having, in fact, a certain period of vibration. This 

 distension, therefore, disappears at one point and passes on to the next at a rate 

 depending on this period of vibration. Details of the form of the pulse wave 



FIG. 234. PORTRAIT OF CARL LUDWIG. 



have not sufficient general interest to warrant description here, although they have 

 considerable practical importance, as indicating states of the heart and blood 

 vessels. It must be clearly understood that the wave of distension travels along 

 the arteries at a much faster rate than the blood current itself. That the 

 progression of a wave is independent of the current of the fluid itself is well 



