Observations on venous pressures and their relationship to capillary pressures / by W.M. Bayliss and E.H. Starling.

  • Bayliss, William Maddock, Sir, 1860-1924.
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Observations on venous pressures and their relationship to capillary pressures / by W.M. Bayliss and E.H. Starling. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    were raised to normal, i.e. if during splanchnic stimulation equals 7 mm. Hg, then p (c) during the same time would be 9 mm. Hg—so that we should have a fall of capillary pressure, although the arterial pressure is raised and the venous remains constant. As a rule however it is found that the portal vein pressure is raised above normal, and may rise to 12 mm. Hg. Under these circumstances p (c) would be 14 mm. Hg, and would be practically unchanged. So that we may have a rise of pressure on both arterial and venous sides without any corresponding rise of capillary pressure. And if we had taken the capillary pressure at 20 mm. Hg instead of 13 mm., there would be an actual fall of capillary pressure during splanchnic stimulation in spite of the simultaneous rise in arteries and veins. In fact in this case there are too many unknown factors to be certain of the presence or direction of any change in capillary pressure. Exactly the same difficulty is met with in the converse case, namely a fall of one or both pressures associated with a dilatation of the arterioles. Here as in the former case the determining factor will be the change in the velocity of the blood current produced by the altered circumstances. We may have a fall of capillary pressure, or the diminution of resistance may more than counterbalance the fall of pressures, so that the capillary pressure will be increased. We consider a special case of this description later on (Effects of section of the cord). A fall of either or both pressures associated with arterial constriction will of course diminish capillary pressure; and the converse case, a rise of arterial or venous pressure or of both, associated with arterial dilatation, will cause an increase in the capillary pressure. In our experiments we have estimated the pressure in the femoral artery, in the inferior cava, and in the portal vein. In our earlier experiments, about 20 in number, we measured the pressure in one of these veins together with the femoral arterial pressure. In our later experiments, of which we give the protocols at the end of this paper, all three pressures were recorded simultaneously. In this way we hoped to throw some light on the variations in the capillary pressure produced in the abdominal organs (intestines &c.) and in the liver, by various procedures, such as obstruction of the larger blood vessels, stimulation of the vagi or splanchnics, asphyxia and so on. • Method of experiment. In all experiments, medium-sized dogs were used, varying in weight from about 7 to 11 kilos. These received half an hour before the