THE CIRCULATION OF THE BLOOD 



79 



To terminate the experiment open the right ventricle. The 

 thoracic cavity will quickly fill with blood and the animal will die 

 a quick and painless death, free from any convulsions. 



II. THE APEX BEAT AND THE HEART SOUNDS. 



1. Appliances. A cardiograph, consisting of a receiving tambour 

 and a recording tambour (Fig. 44). 



The receiving tambour should be about 4 cm. in diameter and 

 not less than 1 cm. deep. The tambour membrane should be of 

 dentists' rubber-dam and should be stretched tightly enough to 

 give it a resistance about equal to that of the relaxed biceps muscle. 

 Upon the middle of the membrane a small cork (1 cm. long) is 

 glued. 



FIG. 44 



The cardiograph : R, receiving tambour provided with a rubber membrane (TO) and a cork, | 

 button (B) to be placed on the apex beat. The receiving tambour is joined through the rubber 

 tube R to the tracing tambour T, whose lever (L) records the movements of the thoracic wall 

 upon the kymograph K. 



The recording tambour should be 3 cm. to 5 cm. in diameter and 

 not more than 3 mm. in depth. The tracing lever should be at 

 least 20 cm. long and provided with a delicate celluloid or parch- 

 ment tracing point. The recording tambour should be mounted on 

 a light chemical stand and held by a universal clamp holder. 



The two tambours should be joined through a piece of pressure 

 tubing two feet in length. 



For construction of tambours see Appendix, 12. 



Besides the cardiograph one will need a chronograph, a kymo- 

 graph, and a stethoscope. 



