“…Collagen fibrils are not suitable for functioning as a barrier against the blood stream, because every contact between blood and collagen fibrils results either in extensive platelet adherence (Bounameaux, 1959(Bounameaux, , 1961K jaerheim and H ovig, 1962;H ughes, 1962;H ovig, 1962, 1963a, 1963bSpaet et al, 1962;Z ucker and Borelli, 1962) or in activating the Hageman factor (Niewiarowski et al, 1965) with consecutive blood coagulation, i.e. fibrin formation.…”