Abstract
The principal factors determining the distribution of fluid between the blood and tissue spaces seems to be the filtering pressure of the blood in the capillaries tending to force fluid out, and the greater osmotic pressure of the colloids of the blood tending to pull fluid in. Normally, these two factors balance one another and the concentration remains fairly constant. As far as experiments go, the capillaries seem to be readily permeable to most crystalloids, especially salts.
The balance described above, however, is easily upset. Thus a rise of capillary pressure leads to a concentration of the corpuscles in the blood due to the filtering out of fluid (Scott 1 ). Starling 2 showed the capillaries in the liver are the most permeable to colloid, the percentage of protein in liver lymph being practically that of the plasma. Histologists almost describe the capillaries in the liver as being devoid of a wall but they are not clear as to the origin of the lymphatics in that organ. With this very permeable membrane the influence of filtration should therefore be most marked in that organ, and this has been shown to be the case (Scott 1 , Lamson and Roca 3 ). The opposite conditions occur when capillary pressure is lowered; that is, the osmotic pressure of the colloid gains the upper hand, fluid is pulled into the vessels and the blood diluted (Scott 1 ). The fluid which is pulled in is in all probability nearly pure salt solution, that is, it contains only a little colloid (Scott 4 ). Seeing that the liver capillaries are so permeable to colloid, one would not expect the colloids of the blood to exercise much osmotic effect in that organ, but it was decided to test the point.
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