The potential oscillations appearing in the olfactory epithelium, nerve and bulb were studied in the toad and the frog.
1. Characteristic potential oscillations were found very frequently in the olfactory epithelium of the toad and the frog. They appeared superimposed on the on-or the off-slow potential at the onset or the cessation of olfactory stimulation.
2. The olfactory nerve and bulb show potential oscillations in response to odour stimulation. They are mutually identical in frequency, phase and shape.
3. The oscillations in the olfactory epithelium are entirely different in frequency, magnitude, shape and time of appearance from those in the olfactory nerve and bulb. It was concluded that there are two kinds of potential oscillations in the lower olfactory nervous system.
4. The potential oscillations in the olfactory bulb of the toad and the frog were compared with those in mammals. The origin of the oscillation was considered.