The recovery curve of excitability that follows an excitation in smooth muscle of the ureter of guinea-pig is examined. The responses such as action potentials and contractions of muscle recover earlier than the conduction velocity. In spite that the contraction curve has summation when a test shock is given in the relative refractory period, no action potentials are recorded from the leading electrode which is placed about 7mm. far from the stimulating point. When the excitability recovers slightly, the small slow potential change is recorded and after the complete recovery normal pattern of action potential is obtained. This fact shows that the excitation is conducted decrementally in smooth muscle when that muscle is in the state of refractoriness. Also from the patterns of action potentials recorded at several stages of relative refractory period, it was assumed that the excitation is conducted from cell to cell through protoplasmic bridges by the electrical variation. This variation is characterized by a slow potential wave. The effects of acetylcholine, adrenaline, histamine and pilocarpine on the patterns of action potentials are also examined.

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The visual center responses to light flash, especially variable with respect to color, were recorded from the tectum opticum contralateral to the illuminated eye in two fresh water fishes, Carassius auratus (L.) and Anguilla japonica T. et S.
1) The photopic response in Carassius to white light flash consisted of two components, a series of spike potential with positive electric sign which represent the potential changes caused by the synchronous volley of nerve impulses passing along the optic tract, and the slow long-lasting negative components (PSP 1, PSP2) which represent the post-synaptic potential. As the characteristics of the response in the dark-adapted fish, the ripple 5 was pronounced and was immediately followed by the sharp negative component, and the PSP 2 did not appear. The response of the photopic Anguilla to the same flash may consist of the PSP 2 only.
2) The pattern of the response in Carassius differs according to the wavelength of the stimulating light but is independent of the intensity of the light, showing the selective appearance of the ripples followed by the post-synaptic components in response to the concerned colored light; whereas no characteristic differences among the responses to various colored lights were observed in Anguilla, revealing the PSP 2 only in response to any colored light.
3) The pattern of the response from the middle part of the tectum in Carassius shows maximal amplitude and appears to be summation of the potential changes from both of inner and outer sides of the tectum of the dorsal aspect of the hemisphere. This was observed in the response to white light flash and also red.
4) The retinal responses and the action potentials of the optic tract in response to white and various colored light flashes were recorded, and were considered with respect to the correlation to the central responses. 5) The possible correlation between the generation of the second surface negative component in the central response (PSP 2) and the abrupt inhibition of the afferent volley of optic nerve impulses was suggested.

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1) The visual center responses to optic nerve stimulation were recorded by the active electrode leading from the surface of tectum opticum in fishes, chiefly Carassius auratus (L.), typifying the diurnal fish, and Anguilla japonica T. et S. as the nocturnal fish.
2) The maximal response in Carassius consisted of the surface negative potential having two components following a surface positive deflection. The later component of the surface negative potential (P 2) has higher threshold than the early component's (P 1). On the positive deflection was superposed two negative spikes representing the action potentials of the pre-synaptic optic nerve fibers. Judging from the results with procaine treatment and with microelectrode recording, the surface negative potential was assignable to the postsynaptic potential.
3) The response in eel was made up of only the P 2 as the post-synaptic component.
4) The topographic variation in the pattern of the response to the optic nerve stimulation took place by a similar manner as those in the response to illumination of the eye with respect to the appearance of the two components of the post-synaptic potential. Dominant appearance of the P 2 was at the inner side of dorsal aspect of the tectum, and that of the P 1 was at the caudo-lateral region.
5) Considering the above two findings and the results on the response to photic stimulation reported previously (1960), it is inferred that the P 1 and the P 2 may correspond to the two post-synaptic components caused by the illumination of the eye, the PSP 1 and the PSP 2 respectively.
6) The two components of the post-synaptic potential may represent the activities of different groups of neurons within the center having different physiological nature.
7) The post-synaptic potentials failed to follow the repetitive stimuli with the intervals below the absolute refractory period, but the cessation of the stimulation evoked a response. The response induced by the cessation of repetitive stimuli (off-response) increased its size as the intervals of stimuli were decreased, whereas the response following the first stimulus (on-response) tended to be inhibited.
8) The P 1 had lower threshold in response to the first stimulus of repe titive stimulation, whereas the P 2 at the cessation of the repetition.
9) The mechanism of the generation of the delayed post-synaptic potential caused by the illumination of the eye (PSP 2) as reported previously (1960) was discussed in the light of the present results.

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The afferent impulses from the single splanchnic nerve fibers during mechanical stimulation of toad's viscera have been studied by means of oscilloscopic recording. The results are summarized as follows:
1) In general it was recognized that a single myelinated afferent fiber innervated in common two or more different organs.
2) The range of diameter of myelinated afferent fibers was 3 to 14-E including myelinsheath.
3) In the viscera of toad two types of adaptation were found in mechanoreceptors. The one was rapid-adapting and the other slow-adapting.
4) The receptive fields which were supplied by a single fiber were relatively large as compared to that of the skin nerve fiber

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1. Employing toad's single myelinated nerve fibres as material, the electrical activity as modified by aniso-osmotic (particularly hypertonic) solutions was investigated.
2. Decrease in magnitude of action current, rise of threshold and remarkable prolongation of action duration were observed.
3. The maximal local response in hypertonic solutions is much larger than that in normal Ringer.
4. Anode break excitation is easily elicitable in hypertonic media.
5. Some microscopic signs, probably indicating hydration or dehydration, were obtained.

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The activity of the pupillo-constrictory centers has been investigated by recording the action potentials in the short ciliary nerve or in the centers of the cat.
1) A. single active unit of the short ciliary nerve in the cat shows in most cases a tonic activity consisting of impulses of 4-10 per second. In the monkey similar activity is also recognized.
2) The completely deafferenated pupillo-constrictory centers are enable to discharge spontaneous impulses similar to those before the isolation of the midbrain.
3) The increased electrical activity of the short ciliary nerve, lasting for the duration of illumination and adapting slowly, is produced by the retinal light illumination. The more the intensity of the stimuli, the greater the impulse frequency becomes, and with the strong illumination the prolonged after-discharges are observed.

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The activity of the cilio-spinal centers has been investigated by recording the action potentials in the long ciliary nerve of the cat.
1) A single active unit of the long ciliary nerve shows a tonic activity consisting of impulses of 1-2/sec.
2) The cilio-spinal centers isolated completely from other central nervous systems and the afferent nerves are able to discharge autochthonous impulses.
3) The impulse discharge from the isolated cilio-spinal centers is inhibited by intravenous administration of adrenalin, but accelerated by asphyxia.
4) The spontaneous discharges led from some fibers of the long ciliary nerve are reflexly inhibited by retinal light illumination, and the inhibitory response becomes remarkable with the increase of the light stimulus, whereas the impulse discharge led from other fibers remains unchanged. The former is the fiber innervating the radial muscles of the iris and the latter is probably the fiber innervating the ocular arteries.

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The electrical response of the snail retractor muscle elicited by stimulating either the muscle or the nerve was recorded. In both cases the response is found to be composed of two component potentials, the fast potential, which is often recorded as a diphasic form, and the slow monophasic potential. The former is attributed to the muscle action potential and the latter to the neuromuscular junctional potential, because the former shows refractoriness after the preceding response, and the latter summates when two stimuli are delivered to the nerve or the muscle with an appropriate interval. The response to indirect stimulation shows depression in the magnitude of the response after the preceding stimulus, and this depression persists for as long as a few minutes. When the test stimulus of just suprathreshold strength is applied to the nerve, this fails completely to elicit any response about 100 msec. after the conditioning response.

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1. The action potentials produced by olfactory stimulation were recorded in the olfactory epithelium, nerve and bulb of a toad and a frog.
2. Besides the on-response, the on-off-and off-responses were found in these tissues in response to olfactory stimulation.
3. In the light of histological findings, mechanisms which produce the three types of responses were considered. It was presumed that except an on-element, there exists an off-element in the olfactory epithelium which responds only to the cessation of stimulation.

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The authors observed the action of GABA on the cerebral cortex of rabbits and cats. Our interest was focused especially on the relation between the action of GABA and strychnine.
1. GABA induced sometimes spontaneous surface positive waves in the cerebral cortex and its action was facilitated by strychnine.
2. Among the isomers of GABA, β-aminoisobutyric acid had a similar action, but α-amino-n-butyric acid and α-aminoisobutyric acid had not such effect.
3. GABA enhanced the amplitude of the initial positive component of strychnine spike at a low concentration and inhibited the second negative component at a higher concentration. As a result, phase reversal was observed in the polarity of strychnine spike.
4. Phase reversal in strychnine spike was limited to the neighborhood of the spot where GABA was applied and GABA could not inhibit spreading of strychnine spike from strychninized site to other spots.
5. Unrelatedness of phase reversal itself to the inhibition on corticifugal impulses was demonstrated.
6. Phase reversal in the polarity of strychnine spike was likewise induced by systemic or intraventricular GABA. The differences of the action of GABA between topical and these administrations were investigated.
7. GABA inhibited a facilitatory effect of strychnine on the secondary negative wave of the direct cortical response and augmented the amplitude of its positive component.
8. GABA counteracted the specific facilitatory effect of strychnine on the negative component of the transcallosal response. On the contrary, GABA facilitated its positive component and generated a late negativity. The discharges of the neuronal elements which were facilitated by GABA were synchronized by strychnine.
9. The effects of various corticipetal impulses on strychnine negative spike and strychnine-GABA positive spike were investigated.
10. The mechanism of the action of GABA was discussed in some details.Anyhow, some antagonistic action between GABA and strychnine on the superficial cortical elements and some synergetic action between them on the deep elements were demonstrated.

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