68 



ENDOCARDIAL PRESSURE. 



Fig. 48, A, gives the result obtained when one elastic bag was placed in the right auricle, 

 being introduced through the jugular vein and superior vena cava; B, when the other bag 

 pushed through the tricuspid oritice was in the right ventricle ; D, in the root of the aorta, pushed 

 id through the carotid ; C, 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. 



Methods. (1) 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 



Right Auricle. 



Right Ventricle. 



Left Ventricle. 



Cardiac Impulse. 



Fig. 48. 

 Curves obtained from the heart of a horse by the cardiac sound. 



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 communicating with it is connected with a Marey's tambour (fig. 47), 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 contraction the auricles 

 relax, or whether the ventricles are contracted while the auricles still remain slightly 

 contracted, so that the whole heart is contracted for a short time at least. The 

 latter view was supported by Harvey, Donders, and others, while Haller and many 



