The conception of viscosity as action per unit volume is used in the analysis of the flow of a suspension or macromolecular solution in a tube. The flow mechanism adduced involves the postulation of molecular vortices of which the suspended particles or molecules form the nuclei. This mechanism is used as a basis for the derivation of a relationship between the specific viscosity of the suspension and the linear dimensions of the vortices. The laws of Einstein, Staudinger, Huggins and their co-workers are derived simply and as special cases of this relationship. The law relating viscosity with concentration is also derived with reference to the same mechanism. This law assumes the form η_sp = an + bn² where a and b are constants and η_sp and n are respectively the specific viscosity and molecular concentration of the solution. It is shown to be in good agreement with typical experimental results. The effect of the aspect ratio of the suspended particles or molecules is also considered and it is shown that the longest particle dimension rotates in a plane normal to the vortex axis. Although no quantitative relationship between viscosity and velocity gradient has been derived the mechanism is observed to lead to results in qualitative agreement with the experimental data.