A manual of human physiology, including histology and microscopical anatomy, with special reference to the requirements of practical medicine . eady stated, the arterial pressuredepends on the condition of the central organ—the heart—and on theperipheral organs—the small arteries. If the action of the heart bearrested, then the blood-pressure rapidly falls. Fig. 78 shows theeffect on the blood-pressure, of arresting the action of the heart, bystimulation of the peripheral end of the vagus. There is a suddenfall of the arterial pressure, as shown by the rapid fall of the curvefrom a]. For the e
A manual of human physiology, including histology and microscopical anatomy, with special reference to the requirements of practical medicine . eady stated, the arterial pressuredepends on the condition of the central organ—the heart—and on theperipheral organs—the small arteries. If the action of the heart bearrested, then the blood-pressure rapidly falls. Fig. 78 shows theeffect on the blood-pressure, of arresting the action of the heart, bystimulation of the peripheral end of the vagus. There is a suddenfall of the arterial pressure, as shown by the rapid fall of the curvefrom a]. For the effects of the nervous system upon the blood-pressure, see Vase-motorCentre (vol. ii.) Pathological.—In persons suffering from granular or contracted kidney andsclerosis of the arteries, in lead poisoning, and after the injection of ergotin, whichcauses contraction of the small arteries, it is found, on employing the method of BLOOD-PRESSURE IN THE CAPILLARIES, 173 v. Bascb, that the blood-pressure is raised. It is also increased in cases of cardiachypertrophy with dilatation, and by digitalis in cardiac affections, while it falls. Fig. 78. Blood-pressure tracing taken with a mercurial kymograph from the carotid of arabbit; o - x, abscissa; vagus nerve stimulated between the vertical lines,a and b. after the injection of morphia (Kristeller). The blood-pressure falls in fever(Wetzel), a fact also indicated in the sphygmogram (§ 69). In chlorosis andphthisis the blood-pressure is low (Waldenburg). 86. Blood-Pressure in the Capillaries. Methods.—Direct estimation of the capillary pressure is not possible on accountof the smallness of the capillary tubes. If a glass plate of known dimensions beplaced on a portion of the skin rich in blood-vessels, and if it be weighted until thecapillaries become pale, we obtain approximately the pressure necessary to over-come the capillary pressure. N. v. Kries placed a small glass plate (Figs. 79, 80)25 - 5 sq. mm., on a suitable part
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