242 



PHYSIOLOGY OF THE HEART. 



[CH. xx. 



pressure iu the ventricle, which t is shown at A' in the second 

 tracing, and produces also a slight impulse, which is indicated by 



Fig. 241. Apparatus of MM. Chauveau and Marey for estimating the variations of 

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



A?' in the third tracing. The closure of the semilunar valves 

 causes a momentarily increased pressure in the ventricle at D', 



affects the pressure in the auricle 

 D, and is also shown in the tracing 

 of the impulse, D". 



The large curve of the ventri- 

 cular and the impulse tracings, 

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

 are caused by the ventricular con- 

 traction, while the smaller undula- 

 tions, between B and c,~ B' and c', 

 B" and c", are caused by the vibra- 

 tions consequent on the tightening 

 and closure of the auriculo-ventri- 

 cular valves. 



Much objection has, however, 

 been taken to this method of in- 

 vestigation. First, because it does 

 not admit of both positive and 

 negative pressure being recorded. 

 Secondly, because the method is only applicable to large animals, 

 such as the horse. Thirdly, because the intraventricular changes 

 of pressure are communicated to the recording tambour by a 

 long elastic column of air ; and fourthly, because the tambour 

 arrangement has a tendency to record inertia vibrations. Rolleston 



Fig. 242. Tracings of (i), Intra-auri- 

 cular, and (2), Intra-yntricular 

 pressure, and (3), of the impulse of 

 the heart; to be read from left to 

 right; obtained by Chaureau and 

 Marey's apparatus. 



