Author applied the vibration of 2, 400p. min., with the amplitude 0.5 mm., to guineapigs which were confined on a plate of the vibrator in free postures.
The guinea-pigs received two or four hours of vibration a day and it was dayly continued to make the total duration: 10, 20, 30, 40, 50, 60, 80, 100 and 160 hours for nine groups respectively.
As this vibrator produced a noise of fifty db., the author made other groups of guinea-pigs receive the noise of the vibrator without the vibration, which provided a series of nine control groups.
The number and duration of rotary nystagmus of the ten hours group were reduced a little after the experiment and in company with the increase of experimental hours, the percentage of reduction augmented, even to 15 per cent. for the 160 hours group. The percentage of reduction for the control groups was in most cases less than the experimental groups.
As for Preyer's auricular reflex, 10 hours actual vibration effected a reduction of 27 per cent, in strength, while corresponding noise without vibration caused that of 10 per cent. compared to the original value before the experiment; and the longer the hours of experiment the more pronounced reduction was obtained, which amounted to 50 per cent, for 160 hours application equally for both expriment and control groups. When comparison was made between the actual vibration groups and the noise experiment (control) groups, more pronouced effect was generally observed in the former than the latter.