From its pharmacological action, thebaine, a kind of opium alkaloid, should be classed in the group of spasmodic poisons, but the writer has already reported that when it was changed into oxycodeinone by oxidation and into dehydrooxycodeinone by hydration, spasmodic peripheral action decreased, and instead, a paralysing action of the cerebruur and the spinal cord became remarkable just as in morphine. In order to determine, through the tail-raising reaction of mice, whether these chemical treatments added to thebaine and its derivatives, caused any change in their actions, he made further experiments. The following are the results: 1. If the amount of injection of thebaine, oxycodeinone, and dehydrooxycodeinone (mg.) per 20g. body weight is indicated by M, and the duration period of the tail-raising reaction, by T, the relation between the two can be represented by the curved-line formula previously suggested by Terada and Honda. 2. The constants obtained are: Thebaine T=236, 59 M1, 068 Oxycodeinone T=1862, 1 M2, 65 Dehydrooxycodeinone T=498, 78 M0, 68 3. Although constant P in thebaine and oxycodeinone is P>1, that in dehydrooxycodeinone becomes P<1. They resemble morphine and heroine which paralyse the cerebrum and the spinal cord. [cf. original (Japanese) P. 168.]