THE NEGATIVE PRESSURE IN THE HEART. 27 



He attached a rubber bag to a tube and filled it with water. By a second 

 tube the bag was put in connection with a minimum manometer. On strongly 

 compressing the bag, and driving the water out, a negative pressure equal to 

 80 mm. Hg appeared. This is due to the momentum of the fluid, which escapes 

 more rapidly than the walls of the bag can follow. If this be so in the heart, 

 it is clear that the negative pressure should also be found in the root of 

 the aorta, for the momentum of the blood would carry it on beyond the 

 ventricle, de Jager l has controverted this explanation by recording an 

 aortic pressure of 130 mm. Hg occurring at the same instant as a pressure 

 of 36 mm. Hg in the left ventricle. Moreover, in all the curves of intra- 

 ventricular pressure, the negative pressure occurs after the closure of the 

 semilunar valves. 



Porter 2 has investigated this difficult subject by means of his 

 minimum manometer in combination with a Hiirthle manometer. The 

 intraventricular cannula was connected by a T-tube to both these 

 instruments. He found that the 

 negative pressure in the left ven- 

 tricle is sometimes entirely absent ; 

 often slight, occasionally great. 

 With the thorax open, in five out 

 of fifteen experiments no negative 

 pressure was observed. In one out 

 of six experiments with the thorax 

 closed there was no sign of a nega- 

 tive pressure. The minimum varied 

 from to - 58 mm. Hg. Some- . . FlG - 18 - 



times, when the heart was beating ?.' cafotid pulse'. 



wpll anrl -nnwprfnllv nn npo-ativp In the auricular tracing, ab is the auricular sys- 

 my, 1 liegdlive tole . bc the thrust outwards of the auriculo- 



preSSlire Was apparent ; While, On ventricular valves, or slight regurgitation of 



. , , , blood at the commencement of ventricular 



the Other hand, a Considerable systole ; cd the negative pressure produced 



negative pressure was often present *& *?3StS SfJSSrfcSSS: 

 in the left ventricle without any J^V*.* S5*TV*?3SSJ S 



SynchrOllOUS Sign of negative preS- auricle from the veins. The coincident points 



j_i i AiT -i a l on the carotid tracing are similarly marked. 



SUre in the leit auricle. OO alSO in At the point d, where the downstroke of intra- 



thp tvarino- fpVpn hv "FYprlpriVn nf ventricular pressure is taking place, the auricular 



me tracing taken oy . icq en pressure is just beginning to rise, 



the right auricular pressure, there 



is no fall below zero synchronous with the period of negative pressure in 



the right ventricle. 3 



According to Porter, the negative pressure in the ventricle has no 

 appreciable effect on the filling of the heart. He explains this anomaly 

 on the following grounds : 



The ventricular negative pressure may occur so rapidly and last so 

 short a time that it is almost over before the auriculo-ventricular valves 

 can open. The cavity of the closed and relaxing ventricle need become 

 but a few cubic millimetres larger than its contents, in order to produce 

 a great negative pressure, just as the suction of a very few drops 

 of fluid from the cannula has a great effect on the manometer. 

 If this be so, the entry into the ventricle of the smallest quantity 

 of blood from the auricle, would abolish the negative pressure. As 

 the auricle stands in open connection with the veins, so slight a 



1 Arch.f. d. gcs. PhysioL, Bonn, 1883, Bd. xxx. S. 506. 



2 Journ. PhysioL, Cambridge and London, 1892, vol. xiii. p. 544. 



3 "Trav. du labor, de Liege," 1888, tome ii. p. 116. 



