The capillary flow of fluid and plastic materials that do not obey Poiseuille's Law has been subjected of recent years to very intensive study, and many hypotheses advanced which attempt to characterize the resistance to deformation of such materials. There is, however, a possible type of resistance which does not appear to have been previously considered, and which it is the purpose of this paper to discuss: a resistance which is a function of the strain, or amount of deformation already experienced. While it is probable that such an effect, when it occurs, is small, the question is of importance in connection with structural studies (e. g., of colloids), which are the occasion of many investigations of plastic or pseudoplastic flow.