240 



PHYSIOLOGY OF THE HEAKT 



[CH. XXL 



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

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



Screw to regulate elevation of lever. 



Writin 



lever. 



I 



Tambour. 



Tube of cardiograph. 



FIG. 218. Marey's Tambour, to which the movement of the column of air in the first tambour is con- 

 ducted by a tube, and from which t is communicated by the lever to a revolving cylinder, so that 

 the tracing of the movement of the impulse beat is obtained. 



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 



FIG. 219. Cardiogram from human heart. The variations in the individual beats are due to the 

 ^.influence of the respiratory movements on the heart. To be read from left to right. 



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 

 apparatus. There are several methods by which the intracardiac 

 pressure may be recorded. 



By placing two small india-rubber 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 



