Abstract: This investigation was carried out on dogs and rabbits under pentobarbital sodium and urethane anaesthesia. Sinomenine, injected intravenously, brought about a temporary excitation of the animal intestines in situ. This excitation was completely dissipated either by application of diphenhydramine or ganglionic blocking agents, partly or completely by atropine, but was not dissipated by bilateral vagotomy. In dogs, gastric secretion and its acidity were increased after a single intravenous in- jection of sinomenine, but the digestive power did not show any significant change. It was found that the histamine level of plasm incressed while that of the skin de- creased after injection of sinomenine. At the same time, the formation of lymph in- creased. According to these results, it is likely that the mechanism of excitation of the animal intestines in situ was chiefly connected with the release of histamine by sinomenine.