Applications of the lagged normal density curve as a model for arterial dilution curves.

• The dispersion of an indicator in a flowing liquid increases with time and with the distance travelled. The form of the dispersion and its rate of increase have only recently come to the attention of investigators. Poiseuille's model, parabolic flow, has been used as an approximate description of flow in the vascular system in spite of the fact that there are a priori reasons for expecting it to be unsuitable. The observations by Griffiths, Hull and Kent, and G. Taylorwere that spatial dispersion of indicator in fluids flowing through rigid tubes was symmetric and nearly Gaussian. Sheppard had arrived independently at the hypothesis that this might also be true for the vascular system and had begun a series of experiments using the random walk equation as a model.