NOTATION x, The dose of a preparation injected into an animal. t, Time. y, Any variable dependent upon x or t. ȳ, The mean of a group of determinations of y at a given value of x. α, The standard interval (see p. 199) of a logistic curve. β, The distance of the point of inflexion of a logistic curve from the origin. Y, The number of standard intervals equivalent to y (see p. 222). X, x/α, the dose when the standard interval is taken as unity. B, β/α, the distance of the point of inflexion from the origin when the standard interval is taken as unity. X0, (β—x)/α, or B—X. t, (β—t)/α, analogous with X0. L, The limiting value of y in a logistic curve. yp, ȳ/Lw, Any weighr factor. n, The number of animals in a group.