The author investigated experimentally effect of the Japanese mineral waters (19 thermals and 6 cold springs) and 20 kinds of salt solutions upon the isolated small intestine of rabbit by Magnus' method. Most waters showed a tendency to decrease the longitudinal tonus and the amplitude of the pendulum movement, but a few showed an increasing effect on the amplitude of the pendulum
movement. Only few kinds of waters, for example acid vitriol springs and sulfated calcium springs,
had an effect characteristic of their chemical classification. Therefore the effect of minesal waters must be judged with the synthetic consideration on the total action of their whole constituents. Concerning the natural radioactive waters in Japan studied this time no peculiar effect was recognized.