50 THE CIRCULATION OF THE BLOOD 



(3) Regularity, which tells whether the heart is regular 

 in either its force or rhythm. 



(4) Its strength, which tells as to the force with which 

 the heart is acting. 



(5) Its length, whether the beat is long or slow and con- 

 tinuous. 



(6) The condition of the vessel wall, whether sclerotic 



FIG. 31. Dudgeon sphygmograph. 



or not. In the study of the pulse an instrument called the 

 sphygmograph is used, which receives the impulse from a 

 beating artery and transmits it by means of a finely ad- 

 justed lever to a smoked surface of paper. Thus a graphic 

 representation of the impulse .is given, the height to which 

 the writing end of the lever goes denoting the force of the 

 impulse of the heart beat at the time of the writing. 



