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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    sents the fall of pressure in arteries, h to c from arterioles to capillaries, and c to d from capillaries to trunk of portal vein. We will assume in the first place that the resistance from c to d does not vary. The fall of pressure from c to d will be then directly proportional to the velocity of the blood from c to d. On stimulation of the splanchnic nerves there is a constriction of the arterioles and therefore a greater fall of pressure from h to c, and a less How of blood through the system. The pressures both at c and d will be diminished. In consequence of the constriction however the general arterial pressure is raised. This rise is not sufficient to drive the normal amount of blood through the resistance and therefore p (c) and p (d) will be still below normal. Now if we put in sufficient resistance at d the rate of fall of pressure will be altered and we may by this means increase bothp(c) and|j(c?) not only to normal but above normal value. In the body such a resistance is interpolated on stimulation of the splanchnics, since a constriction of the hepatic branches of the portal vein is thereby produced. We observe in fact on stimulation of the splanchnics, a rise of pressure in the portal vein as well as in the systemic arteries. Will this increased resistance in tlie liver raise the capillary pressure to normal or above normal ? The factors on which the answer to this question depends will be made clearer if we take numerical values for the various pressures. p (d) normally is equal to 7 mm. Hg. If we assume that the resistance from c to c? is equal to that presented by the liver capillaries, we may take p (c) as 13 mm. Hg. This fall of pressure is proportional to the velocity of the flow from c to d. On stimulation of the splanchnics, v. Basch has shown that the flow of blood from the portal vein is diminished to J of what it was before. The fall of pressure from c to c? is therefore also diminished to one-third of what it was before, and is reduced from 6 to 2 mm. Hg. If in consequence of the increased resistance in the liver, the venous pressure 11—2