CH. XXI.] 



INTKACAilDIAC PEESSURE 



241 



long narrow tubes, in communication with three tambours with 

 levers, arranged one over the others in connection with a registering 

 apparatus (fig. 220), Chauveau and Marey were able to record and 



FIG. 



). Apparatus of MM. Chauveau and Marey for estimating the variations of endocardiac 

 pressure, and the production of the impulse of the heart. 



measure the variations of the intracardiac pressure and the compara- 

 tive duration of the contractions of the auricles and ventricles. By 

 means of the same apparatus, the synchronism of the impulse with 

 the contraction of the ventricles is also shown. 



In the tracing (fig. 221), the inter- 

 vals between the vertical lines represent 

 periods of a tenth of a second. The 

 parts on which any given vertical line 

 falls represent simultaneous events. It 

 will be seen that the contraction of the 

 auricle, indicated by the marked curve 

 at A in the first tracing, causes a slight 

 increase of pressure in the ventricle, 

 which is shown at A' in the second 

 tracing, and produces also a slight im- 

 pulse, which is indicated by A" in the 

 third tracing. The large curve of the 

 ventricular and the impulse tracings, 

 between A' and D', and A" and D", are 

 caused by the ventricular contraction ; 

 while the smaller undulations, between 

 B and c, B' and c', B" and c", are caused 

 by the vibrations consequent on the tightening and closure of the 

 auriculo-ventricular valves. 



Much objection has, however, been taken to this method of 

 investigation. First, because it does not admit of both positive 

 and negative pressure being recorded. Secondly, because the method 



Q 



FIG. 221. Tracings of (1), Intra-auricular, 

 and (2), Intraventricular pressure, 

 and (3), of the impulse of the heart; 

 to be read from left to right; ob- 

 tained by Chauveau and Marey's 

 apparatus. 



