84 A MANUAL OF PHYSIOLOGY 



a controversy which does not even yet show signs of coming to an 

 end, for there is reason to suppose that the character of the curves 

 obtained is to some extent modified by the manner in which the 

 pressure is transmitted. 



Thus, the pressure-curve of the ventricle, according to 

 Hiirthle and those who, like him, have employed manometers 

 with liquid transmission (Fig. 23), remains after the first 

 abrupt rise, which undoubtedly corresponds to the ventricular 

 systole, almost parallel to the abscissa line for a consider- 

 able time, and then descends somewhat less suddenly than 

 it rose. This systolic ' plateau,' although usually broken by 

 minor heights and hollows, perhaps due to inertia oscilla- 

 tions of the liquid or the recording apparatus, would indicate 

 that the ventricular pressure, after reaching its maximum, 



FIG. 23. SIMULTANEOUS RECORD OF PRESSURE IN LEFT VENTRICLE (v) AND 



AORTA (A). (HURTHLE.) 



The tracings were taken with elastic manometers ; o indicates a point just before the 

 closure of the mitral valve ; i, the opening of the semilunar valve ; 2, beginning of the 

 relaxation of the ventricle ; 3, the closure of the semilunar valve ; 4, the opening of 

 the mitral valve. The ventricular curve shows a ' plateau." 



maintained itself there throughout the greater part of the 

 systole. The tracings yielded by the best manometers with 

 air transmission (Fig. 24) show the same suddenness in the 

 first part of the upstroke and the last part of the descent 

 that is, the same abruptness in the beginning of the con- 

 traction and the end of the relaxation. But they differ 

 totally in the intermediate portion of the curve, which, 

 climbing ever more gradually as it nears its apex, remains 



