240 PHYSIOLOGY OF THE HEART [CH. XX. 



pause, the tremors at the commencement of which are partly instru- 

 mental and partly caused by the closure of the semilunar valves. 



Another method of obtaining a tracing from one's own heart 

 consists in dispensing with the first tambour, and placing the tube 

 of the recording tambour in one's mouth, and holding the breath 

 though keeping the glottis open. The chest then acts as the first 

 tambour, and the movements of the lever (cardio-pneumatogram) may 



be written in the usual way. 



> 



Intracardiac Pressure. 



The tracings of the cardiograph are, however, very variable, and 

 their interpretation is a matter of discussion. A much better method 

 of obtaining a graphic record of the events of the cardiac cycle con- 

 sists in connecting the interior of an animal's heart with recording 



FIG. 248. Apparatus of MM. Chauveau and Marey for estimating the variations of endocardiae 

 pressure, and the production of the impulse of the heart. 



apparatus. There are several methods by which the intracardiac 

 pressure may be recorded. 



By placing two small indiarubber air-bags or cardiac sounds down 

 the jugular vein into the interior respectively of the right auricle and 

 the right ventricle, and a third in an intercostal space in front of the 

 heart of a living animal (horse), and placing these bags, by means of 

 long narrow tubes, in communication with three tambours with 

 levers, arranged one over the others in connection with a registering 

 apparatus (fig. 248), Chauveau and Marey were able to record and 

 measure the variations of the intracardiac pressure and the compara- 

 tive duration of the contractions of the auricles and ventricles. By 

 means of the same apparatus, the synchronism of the impulse with 

 the contraction of the ventricles is also shown. 



In the tracing (fig. 249), the intervals between the vertical lines 

 represent periods of a tenth of a second. The parts on which any 



