KNPOCARDTAL 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 ; <?, 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 ampulla?, 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. 



Bight Ventricle. 



Left Ventricle. 



Aorta. 



"Cardiac Impulse. 



Fig. 29. 

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



