88 



ENDOCARDIAL PRESSURE. 



through the carotid; 0, pushed past the semi-lunar valves into the left ventricle; 

 while at E a similar bag has been placed externally between the heart's apex 

 and the inner wall of the chest. In all cases v = auricular contraction; V, that of 

 the ventricle; s, closure of semi-lunar valves, sooner in C than B; P pause. 



Method. The cardiac sound consists of a tube containing two separate air- 

 passages, and in connection with each of these there is a small elastic bag or 

 ampulla. One of the bags is fixed to the free end of the sound, and communicates 

 with one of the air-passages. The other bag is placed in connection with the 

 second air-passage in the sound, and at such a distance, that, when the former bag 

 lies within the ventricle, the latter is in the auricle. Each bag and air-tube in 

 connection with it, is connected with a Marey's tambour, Fig. 28, provided with a 

 lever which inscribes its movements upon a revolving cylinder. Any variation 

 of pressure within the auricle or ventricle will affect the elastic ampullse, and thus 

 raise or depress the lever. Care must be taken that the writing-points of the 

 levers, are placed exactly above each other. A tracing of the cardiac impulse is 

 taken simultaneously by means of a cardiograph attached to a separate tambour. 



It has still to be determined whether the auricles and ventricles act 

 alternately, so that at the moment of the beginning of the ventricular 



Eight Auricle. ' 



Eight Ventricle. 



Left Ventricle. 



Aorta. 



Cardiac Impulse. 



Fig. 29. 

 Curves obtained from the heart by the cardiac sound (Chauveau and Marey). 



