Materials and methodsInterstitial fluid pressure (Pif) of the dog was measured from capsules implanted in subcutaneous tissue of the upper and lower hindleg 4 to 8 weeks prior to use. (The capsules were a disk-shaped hollow (6 mm x 9 mm i.d.) porous polyethylene matrix (Bolab, Inc.) with an average pore size of 65 μm.) Total tissue pressure (Ptot) was measured either with small flaccid balloons inserted subcutane-ously or, more frequently, by the needle method for measuring total tissue pressure (see (3) for a discussion of these methods).Pressure transmission was examined in two different preparations. With the first, the intact hindleg of the pentobarbital anesthetized dog was placed up to the hip in a water filled plethysmograph and Pif and Ptot measured while applying positive or negative pressure to the leg. With the second preparation, the hindlimb was totally isolated from the dog and artificially perfused with whole blood as described elsewhere (4). The isolated hindlimb was then placed entirely i...