vii MECHANICS OF THE HEAET 203 



pressure of the auricle and right ventricle, which he gives as 

 typical (Fig. 64), to see that the intersystole does not follow 

 immediately upon simple systole, but on the complete pulsation of 

 the auricle (auricular systole and diastole). 



Since, however, the intersystole coincides with a sharp rise of 

 pressure in the auricle, and since the presence of a sound intro- 

 duced between the flaps of the valves may give rise to a slight 

 reflux of blood from ventricle to auricle, it seems probable that 

 the intersystole depends precisely upon this slight reflux, coincident 

 with the initiation of ventricular systole. 



It is evident from these data that the " intersystolic phase " of 

 Chauveau's tracings represents no real fact, occurring during the 

 normal cycle of cardiac movement, but is in all probability an 

 artefact, coincident with the period of latent systole, artificially 

 prolonged by the presence of the exploring sound in the auriculo- 

 ventricular orifice. 



But if this point in Cbauveau's tracings is difficult to interpret, 

 another feature offers far more insuperable obstacles, i.e. that part 

 of the pressure curve in the auricle which corresponds to the 

 ventricular diastole, which Chauveau passes over, keeping silence 

 on the subject. 



At that period there is in Chauveau's curves an incomprehensible 

 rise of auricular pressure. Now the observations of all other 

 experimenters, carried out by different methods, more reliable than 

 the sound, have, without exception, resulted in showing a negative 

 pressure in the ventricle during the primary phase of diastole. 

 Since in diastole, when the cuspid valves are open, the auricle and 

 ventricle form a single cavity, it is evident that the negative 

 pressure existing in the ventricle must be propagated to the 

 auricle also. 



More interesting and more probable, on account of their 

 simplicity, are the researches carried out by numerous experi- 

 menters on the venous pulse of the cava and jugular veins, either 

 in man or in animals, which throw light on the mode in which the 

 right heart is filled and emptied. 



Among the authors who have more recently been engaged on 

 this subject are Mackenzie (1902), Beccari (1903), Wenckebach 

 (1906), Fredericq (1907). They have recorded tracings of the 

 venous pulse (phlebogram) with a simultaneous record of the 

 cardiac pulse (cardiogram), or of the radial artery (radiogram). 



In nearly all healthy people, in the horizontal supine position, 

 with head and neck a little lower than the body, it is possible to 

 detect with the eye the pulsation at the base of the neck, and to 

 take a tracing of it, by means of a sufficiently sensitive exploring 

 tympanum. In the stage of convalescence from diseases, accom- 

 panied, as in jaundice, by weakening of the heart-beat, it is easy 

 to obtain fairly clear phlebograms, which in their elevations and 



