From the limited data obtained it appears that the substitution of the tropic acid group as it appears in atropine, hyoscyamine, and scopolamine, with a mandelic acid group as it occurs in homatropine, or a benzoic acid group as it occurs in benzoyltropine and benzoyloscine, results in a great loss of activity. In general, there is a rough correlation between inhibition of salivation and effectiveness in swing sickness.