CH. XX.] 



INTRACARDIAC PRESSURE 



241 



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 impulse, which is indicated by 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 ventricular and the impulse tracings, 

 between A' and D', and A" and D", are caused by the ventricular con- 

 traction, 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 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 ten- 



rlonnv fn r^Pnrrl inertia viKrotirma 

 nc y to jrtia VlDraiK QS. 



Eolleston re-investigated the subject 

 with a more suitable but rather com- 

 plicated apparatus. The principle of 

 the method consisted in placing the cavity of a heart-chamber in 

 communication with a recording apparatus by means of a tube 

 containing saline solution. His recording apparatus consisted of a 

 lever connected to a piston ; the upward and downward movements 

 of the piston-rod were due to the varying pressures exerted on the 

 blood by the contraction and dilatation of the heart; the rise and 

 fall of the lever were controlled by the resistance to torsion of a 

 steel ribbon to which it was attached. The following figure (fig. 

 250) shows the kind of tracing he obtained. He found: 



1. That there is no distinct and separate auricular contraction 

 marked in the curves obtained from either right or left ventricles, 



* There can be no doubt that the point D which Marey considered to coincide 

 with the closure of the semilunar valves does not really do so. The closure occurs 

 much earlier (E in fig. 252). 



FIG. 249. Tracings of (1), Intra-auricular, 

 and (2), Intra-ventricular pressure, 

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

 to be read from left to right; ob- 

 tained by Chauveau and Marey's 

 apparatus. 



