268 THE CIRCULATION IN THE BLOOD-VESSELS. [CH. XXI. 



this is near the surface, and supported by bone. It is a most 

 valuable indication of the condition of the patient's heart and 



Fig. 260. Marey's Sphygmograph, modified by Mahomed. 



vessels. It is necessary in feeling a pulse to note the following 

 points : 



1. Its frequency ; that is the number of pulse beats per minute. 



This gives the rate of the heart beats. 



2. Its length ; that is how long a time each pulse-beat occupies. 



3. Its strength; whether it is a strong, bounding pulse, or a 



Fig. 261. Diagram of the lever of the Sphygmograph. 



feeble beat ; this indicates the force with which the heart 

 is beating. 



4. Its regvlarity or irregularity ; irregularity may occur owing 



to irregular cardiac action either in force or in rhythm. 



5. Its tension ; that is the force necessary to obliterate it. This 



gives an indication of the state of the arterial walls and 

 the peripheral resistance. 



