VII 



MECHANICS OF THE HEAET 



201 



VI. In order to comprehend the nature of the evacuation and 

 refilling of the heart, it is important to make an experimental 

 study of the oscillations of pressure within the auricles and the 

 ventricles, in presy stole, systole, and perisystole. 



These observations were first made by Chauveau and Marey 

 (1861) on the horse, by means of the so-called cardiograph 

 sound, in conjunction with a tambour and lever writing upon 

 a rotating cylinder (Figs. 62 and 63). The modifications in 

 instrument and method made by Fick, von Frey, Hiirthle, Eoy, 

 Fredericq, Bayliss and Starling, and Porter, have led to results 

 which differ in certain important points from those of the two 

 French investigators. 



In the original researches of Chauveau and Marey, the tracings 

 of the oscillations of pressure in the right auricle were very 

 imperfect, owing possibly to insufficient sensibility of the elastic 

 ampulla introduced into 

 the said cavity. At the 

 Home Congress (1894), 

 Chauveau corrected cer- 

 tain errors of Marey, on 

 the strength of new 

 cardiographic curves, 

 obtained from the horse 



by means Of lllOre per- FIG. (W. Marey's tambour with writing lever (Verdin's 



PI 1 perfected type). <i, Metal capsule closed by rubber 



leCt exploratory SOUnClS. membrane, attached without tension to metal ring B. 



TMioeo < iliypvvif iim The aluminium disc fixed to the centre of the membrane 



carries a writing lever. Special contrivances make the 



Were published in a instrument more or less sensitive by adjusting the initial 



\. /-, position of the lever, and bringing the writing point nearer 



Series OI memoirs (lbV*y- to or farther from the surface of the moving drum. 



1900), which seem to us 



rather to indicate the unreliability of results obtained with the 



cardiac sound, than to add to the known data of cardiac mechanism. 



Let us examine the most important of these memoirs, that 

 entitled L' Inter systole du cceitr (1900). This Chauveau calls a 

 phase of his cardiographic tracings, interpolated between presystole 

 and systole. 



If the interpretation which he gives of this period, interposed 

 between the systole of the auricles and that of the ventricles, were 

 correct, it would involve a complete revolution in the fundamental 

 concepts of cardiac mechanism. To prove this, it is only necessary 

 to bear in mind the conclusions above stated in regard to the 

 function of the auriculo- ventricular valves. 



These close at the end of presystole, so that they are 

 already shut at the beginning of systole. If, however, we admit 

 an intersystolic phase, then the said valves, not being kept 

 in the position of closure by rise of ventricular pressure, would 

 reopen, and thus render useless the entire apparatus described 

 above for closing them. 



