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March 1959


Author Affiliations

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AMA Arch Ophthalmol. 1959;61(3):505-508. doi:10.1001/archopht.1959.00940090507018

With regard to this article (McEwen, W. K.: Application of Poiseuille's Law to Aqueous Outflow, A. M. A. Arch. Ophth. 60:290-294 [Aug.] 1958), cursory consideration may lead to the conclusion that the so-called "theory of the aqueous flow through the trabecular meshwork" or "Friedenwald's theory" represents a masterpiece sui generis, whereas in reality it is just applied hydrodynamics. Its keystone and fundamental term, "facility of outflow," does not represent a new characteristic but is identical with the classical "coefficient of permeability" or "transmission constant"—called in the pertinent German literature "Durchlässigkeit" or "Hydrogeologische Konstante" to point to the field of practical application, namely, the flow of fluids (water and oil) through porous material (sands, sandstones, and porous rocks), including the flow of water through filter beds for municipal water systems. The unit of the "permeability" or the "facility of outflow" is named 1 Darcy, after the engineer H. Darcy, the author