The minimal certainly emetic vein dose of pilocarpin alkaloid (hydrochloride used) was determined for dogs as 0.7 mg. per kilo. It having previously been observed that atropin was capable of antagonizing the emetic action of pilocarpin, experiments were made to determine the smallest dose of this alkaloid (sulphate used) which was just sufficient to prevent emesis from the minimal emetic dose of pilocarpin. The antagonistic dose of atropin alkaloid was then determined for twice, four, eight and sixteen times the minimal dose of pilocarpin.The results showed that it requires about 1/75th as much atropin base as of pilocarpin base to antagonize the emetic action of the smallest effective dose of the latter. About the same ratio was found for twice the dose of pilocarpin. For four times the minimal dose of pilocarpin 1/95th as much atropin was required; for eight times about 1/125th; and for sixteen times about 1/200th.Similar experiments were made with nicotin and atropin, but the toxicity of the former dru...