APPLICATIONS TO PHYSIOLOGY 277 



the Academy of Science and at the Academy of 

 Medicine a theory of cardiac movement, based upon 

 information derived from the graphic method. This 

 theory, to-day universally accepted, put an end to 

 differences of opinion among physiologists and physi- 

 cians, and it has not been unassociated with recent 

 advances in the diagnosis of cardiac and vascular 

 diseases. 



We were induced to embark on these experiments 

 by the incomplete evidence derived from direct exami- 

 nation regarding the nature and sequence of the 

 extremely complicated movements, executed by the 

 heart from moment to moment during a complete 

 cycle of events. 



Our method was indirect, and consisted in register- 

 ing the curves of pressure variations occurring in the 

 interior of the cardiac cavities as well as outside these 

 chambers. Our -curves, properly speaking, did not 

 explain the movements of the heart ; but, nevertheless, 

 they enabled us to state the order and sequence of the 

 auricular and ventricular movements from the changes 

 in pressure which they expressed. 



This interpretation was often a very difficult task, 

 and required a considerable number of experiments in 

 order to verify the different points at issue. Although 

 it was pretty evident that the maximum of pressure in 

 each cardiac cavity corresponded to the moments at 

 which these cavities contracted for the expulsion of 

 the contained blood, yet it was by no means easy to 

 discover the significance of each variation on the 

 cardiography curves. 



Let us examine tracings which express the 

 alterations in blood-pressure in the auricles and 

 ventricles, and the phases of cardiac pulsation. If 

 these figures were placed before the eyes of a physician, 

 whom we will suppose ignorant of the physiology of 



