

THE CIRCULATION. 939 



Endocardiac Pressure. The ordinary mercurial manometer, by 

 which the heart's work can be estimated, is unsuitable for deter- 

 mining its ventricular pressure. The objections are the relatively 

 great amount of work required to produce a given displacement of 

 the mercury; that it is not susceptible and sensitive to quickly 

 follow differences of pressure; and when once displaced, the mer- 

 cury possesses enough oscillations of its own which confuse oscilla- 

 tions of blood-pressure.- However, when this instrument by the 

 introduction of a properly placed valve is converted into a "maxi- 

 mum and minimum manometer/' the actual blood-pressure may be 

 more readily determined. 



The dog has been very extensively used for the application of 

 this instrument, as a consequence of which the appended figures are 

 given : 



SFSTOLE. DIASTOLE. 



MAXIMUM PRESSURE. MINIMUM PRESSURE. 



Left ventricle 140 millimeters. 30 to 40 millimeters. 



Right ventricle 60 " 15 " 



Right auricle 20 w 7 to 8 " 



By negative pressure is meant that the mercury in the instru- 

 ment has been sucked toward the heart. The negative pressure, as 

 is seen, occurs only during the diastole of the heart. Moens is of 

 the opinion that this negative pressure within the ventricle happens 

 shortly before the systole has reached its height. During negative 

 pressure the blood from the veins is sucked into the heart. 



For determination of the duration of the cardiac events, as well 

 as the blood-pressure that is, to have tracings of the curves for 

 each cavity, to know the time-relations for comparisons, as well as 

 the curves of the great arteries and veins requires an instrument 

 of some complexity. Only within recent years have these been 

 invented, by Chauveau and Marey, whereby elastic manometers 

 counterbalance the blood-pressure instead of a column of liquid. 

 Many of the instruments employed give their tracings from move- 

 ments transmitted to them from cardiac sounds through a tube to 

 the recording apparatus. The sounds were usually appropriately 

 curved cannulae, to one end of which were attached flexible rubber 

 bags, or ampullae. Two were introduced through the jugular vein 

 into the right auricule and ventricle, a third into an intercostal 

 space in front of the heart. These were put into communication 

 with three tambours with their needles, by which were recorded the 



