Abstract
Effect of density and size of particles through the digestive tract of cattle and humans was estimated, using inert plastic particles. An optimum (Maximum passage rate) in density at approximately 1.2 g/cm3 and in size between 20 and 30 x 10-3 cm3 was observed. The excretion pattern of chromic oxide by cattle followed the equation y = abx, in general, but the rate of passage is slower than would be predicted from its size and density. The significance of this equation and of a pronounced shoulder in the excretion curve is discussed.