Selected monographs.

Date:: 1888

Catalogue details

Licence: Public Domain Mark

Credit: Selected monographs. Source: Wellcome Collection.

154/440 (page 136)

13G siderable quantity of serum or dog's blood can be injected witliout any perceptible increase in tbe excretion of urine; on tlie otlier hand, according to Pawlow, the absorption of large quantities of fluids from the stomach produces an aug- mentation of the urinary excretion without any rise in the blood-pressure.^ I cannot conceive that these facts consti- tute any obstacles to the theory of filtration. For, as Heidenhain' himself insists, if, in the first case, when fluid is injected into the blood, the pressure does not rise in the manner previously supposed, it follows that there is, ceteris paribus, no reason why increased filtration should take place : but as regards the diuretic effect of the introduc- tion of fluids into the stomach, in this case the question of the dilution of the blood has to be taken into consideration, for, as we all know, the filtration is very considerably pro- moted by the dilution (see above). As a matter of course the dilution produces the same effect, even when it is not the result of absorption from the stomach. Thus, if instead of serum or blood a dilute solution of chloride of sodium be injected into the blood, a considerable increase in the quan- tity of the urinary excretion would be noticed just as before, and this increase would be unattended by any increase of pressure. If all these considerations do not directly establish the truth of the filtration theory, at all events they do not con- tradict it. But finally, and this is a fundamental point of great im- portance, Heidenhain thinks that, generally speaking, the capillaries are not endowed with any universal capacity for allowing larger quantities of fluid to pass through their coats when the arterial blood-supply is increased, and that the capillaries of the renal glomeruli, on account of their epi- thelial covering, must offer more than usual resistance to the filtration pressure. The latter point, i.e. the gi-eater resistance of a wall covered with epithelium need not be contested, but surely the statement that transudation from the capillaries is independent of pressure and especially of arterial pressure, is contrary to the laws of filtration. In proof of his assumption, Heidenhain appeals to experiments > Ibid., p. 333.