CARDIOGRAM. 241 



3. Trace a cardiogram. The cardiograph consists of two 

 pneumatic tambours connected by an india-rubber tube. 



The tambour for the heart is provided on its rubber mem- 

 brane with an ebonite button, the capsule rests on the chest 

 wall and is secured in position by an elastic girth. 



The recording tambour carries a recorder for writing on a 

 smoked surface. 



The tube which connects the two is provided with a brass 

 valve to regulate the air tension in the system. 



Place the button of the heart tambour over the apex beat 

 on the bared chest of the subject, who is seated on a chair. 



Let the drum revolve at a medium speed, and apply the 

 recorder to its surface and take half-a-dozen curves. Adjust 

 to get a maximum tracing. 



The curve will present four well-marked features : 



(a) A slow rise the heart is distending immediately followed 



by 



(b) A rapid rise the ventricular systole which passes into 



(c) An irregular plateau, at the end of which occurs the 

 closure of the semi-lunar valves. 



(d) A descent the heart loses redundancy. Diastole. 



Next repeat the cardiogram, together with a pulse tracing 

 written beloAv it. Use the sphygrnographic tambour belonging 

 to a Brondgest pantagraph, and adjust it to the wrist over 

 the radial pulse. Fix into place with tapes. The wrist must 

 be supported on a properly shaped pad in a slightly over- 

 extended position. The arm must be unconstrained and the 

 muscles relaxed. Adjust the pressure of the tambour button 

 by means of the screw which regulates the tension of the 

 spring until the maximal excursion of the recorder is produced. 



Let both points write vertically beneath each other. 



