Log-normal distribution of equiefective doses of norepinephrine and acetylcholine in several tissues.

Frequency distributions of equieffective doses of norepinephrine in the rat vas deferens, the perfused artery of the rabbit ear, the aortic strip of the rabbit, the nietitating membrane of the spinat cat and the guinea-pig atrium and of acetylcholine in the rat vas deferens are presented. In all six, the distributions on an arthmetic scale tended to deviate from normal but the distributions on a log scale did not. In the three groups of data with the larger N 's, this deviation from normal of the arithmetic frequency distribution was significant by the Kolmogorov-Smirnov test. It is concluded that the distribution of equieffective doses of agonists is generally normal on a log scale but not on an arithmetic scale. Therefore, the means of equieffective doses and the statistical tests of their significance should be based on mean logs or their antilogs, the geometric means, not on arithmetic means.