VII 



MECHANICS OF THE HEAET 



207 



given here. Both his results and those of Bayliss and Starling confirm the 

 statement that the curve of intraventricular pressure presents a true systolic 

 plateau during the efflux of blood from the heart This important feature 

 of the cardiac function seems, therefore, to be definitely established. 



In perisy stole, too, it is possible to distinguish two periods ; 

 the one shorter, of active diastole, the other more prolonged, of 

 passive diastole or rest of the whole heart. During the former, 

 pressure falls suddenly both in ventricle and auricle, and becomes 

 negative, thus permitting the 

 active refilling of the heart by 

 aspiration of blood from the veins. 

 During the second, the negative 

 pressure rises again slowly in the 

 ventricle and auricle, until at 

 the beginning of presystole it 

 approximates to the zero line: 

 this represents the period of 

 passive filling of the heart, caused 

 by the vis a tergo of the venous 

 blood stream, and the negative 

 pressure in the thoracic cavity, 

 when the experiment is con- 

 ducted with the closed thorax. 



The elastic ampullae and 

 sphygmoscopes of Chauveau and 

 Marey are instruments well 

 adapted for obtaining tracings of 

 the form of the rapid oscillations 

 of pressure that occur within the 

 cavities during the cardiac cycle, 

 but they are inadequate to de- 

 termine the absolute value of 

 the intracardiac pressure. The 

 best method for determining the 

 maximum to which the pressure 

 in the cavities may rise, and the minimum to which it may fall, is 

 that of Goltz and Gaule (1878), which was also employed by De 

 Jager (1883), and consists in fitting to the recording mercury 

 manometer (Fig. 68) a valvular apparatus which closes when the 

 pressure falls, and opens again when it rises, or vice versa, so that 

 the manometer serves as a maximum or minimum manometer. 

 When connected with a cavity of the dog's heart by means of an 

 open sound, the column of the manometer will rise at each systole 

 to a given maximal height, after which it traces a horizontal 

 line (maximum manometer) ; or falls at each diastole to a cer- 

 tain minimum, after which it remains stationary (minimum 

 manometer). 



FIG. 68. Lud wig's mercury manometer (Zim- 

 mermann's type). TheTtoat seen on the right 

 consists of a fine steel rod terminating at the 

 lower extremity in a pointed ivory cone, 

 which dips into the column of mercury, 

 and at the upper extremity in a glass pen 

 tilled with ink, which traces the variations 

 of pressure upon the paper of the revolving 

 drum. 



