Under constant conditions of temperature and light, with food and water always available and without perturbation by periodic noises, individually caged chaffinches (Fringilla coelebs L.) show a clear circadian rhythm of locomotor activity. The period τ is divided in activity-time α and rest-time ρ. Period and activity-time as well as the average amount of activity per 24 hours depend on intensity of illumination. With an increase in light intensity from about 0.2 lux to about 5.0 lux, the period becomes shorter and the activity-time longer. The amount of activity increases more than proportionally to the lengthening of activity-time. These results are in agreement with the circadian rule for light-active animals. They are interpreted in view of a special model. This model describes the discontinuous rhythm of activity and rest by a continuous basic oscillation which passes twice during each period through a threshold. The bird is active as long as the oscillation is above the threshold. Changes in the α:ρ-ratio, in combination with the changes in amount of activity, are explained as changes in the position of the level of the oscillation relative to the position of the threshold. Level and frequency of the circadian oscillation are positively correlated to each other and to the intensity of illumination.

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Transmembrane potential was recorded by the use of a microelectrode inserted into the myocardium in the connected half-ventricle, or in the whole ventricle and a fragment ventricle of oyster respectively and the formation and property of the plateau were studied.
1. The plateau becomes less prominent in consequence of a decrease in size of the material.
2. Size and shape of the plateau frequently change according to the length of delay between action potential spikes recorded simultaneously from two half-ventricles. When the plateau is manifested, the beat interval is prolonged.
3. The preceding action potential obtained from one of the two half-ventricles has a remarkable plateau, more frequently than in the succeeding action potential recorded from the other half-ventricle.
4. Frequently the plateau becomes prominent by electric stimulation applied during the repolarization phase, often followed by hyperpolarization.
5. The small potential induced by the action potential of adjacent fibers sometimes causes a local response of the recorded fiber. Occasionally this induces a noticeable plateau in the action potential of the other half-ventricle.
6. The small potential sometimes elicits the plateau potential on the recorded fiber itself.
7. Frequently plateaus disappear after treatments, such as addition of acetylcholine to the physiological saline.
8. The plateau is considered to be formed not only because of the effect of adequately delayed potential deflection caused by adjacent fibers, but also because of the character of the membrane associated probably with a change in membrane ion permeability.

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Renin activity of the kidney was determined in a strain of Wistar rats which manifest spontaneous hypertensive cardiovascular disease. A decrease of renin activity was found after a latent period of several weeks after the blood pressure had risen. It was concluded that the decrease was a result of blood pressure elevation as a compensatory reaction.

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1. Interrelations between the slow potential sequence and neuron activities in the sensorimotor cortex to the stimulations of thalamic relay (VPL) and nonspecific (VA) nuclei were studied in the rabbit and the results led to the following considerations.
2. The initial positive deflection recorded at the cortical surface is the reflection of the intracortical negative potential which resulted from massive terminal activities in the fastest thalamo-cortical projection fibers and synaptic activities in some cortical neurons firing with short latency and adapting in a short time.
3. The augmenting positive-negative potential is brought about by the deep negative-positive field potential which results from EPSPs and IPSPs generated in many cortical cells and reflects upon the cortex in the reverse sign. In addition, postsynaptic activities in upper layers must participate in the formation of this potential, especially of the negative phase.
4. Gradual synchronization of PSPs produced in respective neuron makes the intracortical field potential larger when stimulated at 8 c/s. While IPSPs developing later, probably owing to the activities of inhibitory interneurons, lower the height of EPSPs and lead to the inhibition or cessation of firings. These are possible mechanisms by which the waxing and waning occur in response to low-frequency VPL stimulation.
5. Less evidence was obtained to allow making the distinct relation between neuron activities and cortical slow potentials to 8 c/s VA stimulation. Therefore, strict ideas on the origins of component potentials in the recruiting response were not obtained. It is reasonable, however, to presume that the same elements and mechanisms as in the augmenting resjcrse alEo take a part in the recruiting response.

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A certain electrophysiological features of the ventricular fiber have been investigated in the papillary muscle of the dog by the use of a special method for polarizing, extracellularly and simultaneously, a large number of its fibers.
1) The electrotonic potential and its spatial decay was found to conform with the cable law as if it were in a single fiber. The space and time constants of the ventricular fiber could be estimated from the slopes of lines denoting interrelationships between the amplitude and the half time of rise of electrotonic potential to distance respectively. The calculated space constant was 1.3 mm, and the time constant was 2.0 msec.
2) The critical membrane potential was -65 mV.
3) The membrane resistance was found to decrease slightly at the peak of spike (to not less than 90% of resting resistance), and to remain about the same during the entire phase of plateau in the resting phase.
4) The action potential in the ventricular fiber could be abolished by anodal current even in the early stage of repolarization. The effectiveness of anodal polarization varied depending on the duration of current pulse and the timing of application: the longer the duration and later its application, the higher was the efficiency for producing the abolition.
5) In general, there seems to be no essential difference in nature of membrane between the ventricular and Purkinje fibers. The observed differences in electrophysiological behaviors between the two appear to be dependent rather on the difference in their fiber architectonic.

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Using unanesthetized cats, investigation of the perception of the sensory information in the CM-neuron was conducted by microelectrodical recording of the spontaneous discharge of the neuron, the driven unitary discharge following stimulation of the peripheral nerve and the action potential of the neuron in response to noxious stimuli. The prerequisite for the CM-neuron was to establish that convergence of the splanchnic and sciatic transmissions existed in the neuron and that the neuron responded to noxious stimuli. The present authors have analysed 82 units of the CM-neuron which fulfilled the prerequisites.The results were summarized in the following way.
The spontaneous discharge of the CM-neuron had a frequency of 5 to 25 per second. The average interval showed 34.1 msec with a standard deviation of 13.8 msec. The deviation was relatively large. The spontaneous discharge did not show a burst-like volley as far as the animal was in an unanesthetic condition. The interval of the spontaneous firing became shortened as the frequency increased in stimulation of the peripheral nerve. When stimulation of 1 cps was applied to the peripheral nerve, the spontaneous discharge of the CM neuron succeeding from the driven unitary discharge increased in firing rate and was facilitated for 550 msec. When stimulation of 10 cps was applied to the peripheral nerve, the driven unitary discharge of the CMneuron did not follow an individual stimulus but the spontaneous unitary discharge was extremely facilitated. The spontaneous firing of the CM-neuron was facilitated in various modes following tetanic stimulation of the splanchnic nerve. The neurons in 59% showed a marked continuous facilitation of the spontaneous firing and some of these neurons showed a facilitation of the spontaneous firing in close relation to the spindle burst of the slow potential.And the neurons in 25% showed a marked inhibition of the spontaneous unitary discharge followed by a phasic facilitation.
The receptive field of the CM-neuron responding to noxious stimuli was very large and covered the part on both sides of the body, extending to more than two limbs. The firing rate of action potential and the duration of after-discharge were different according to the site of the receptive field. The reactability of the CM-neuron to noxious stimuli was augmented to increase the frequency of action potential and to prolong the duration of of terdischarge, following brief train stimulation of the MRF or contralateral CM by 10 cps or 100 cps.
The perception of noxious stimuli was mostly related to the spontaneous discharge of the CM-neuron and supported by excitation in the polysynaptic central core conduction.

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1.Effects of the mesencephalic reticular stimulation were observed on the medullary respiratory discharges of the urethanized rabbits. Both inspiratory and expiratory neurones were facilitated by the medial mesencephalic stimulation.Inhibition was observed during the lateral stimulation. The rate of breathing increased either by facilitation or by inhibition of the respiratory discharges. The action of the midbrain is assumed to cause the simultaneous facilitation or simultaneous inhibition of both inspiratory and expiratory neurones.
2. Respiratory discharges were recorded from the medulla of the urethanized cats during local heating of the preoptic region. With the onset of heating, the respiratory rate and the rate of respiratory discharges are slightly decreased at first and then increased. The mode of the neuronal responses to hypothalamic heating was identical with that of the responses to midbrain stimulation.
3. In the gasping, which resulted from the transection of the rostral medulla, expiratory bursts gave way to a continuous firing in which the discharge frequency remained unchanged. The appearance of inspiratory discharges was inhibited. These figures were similar to those of expiratory responses from vagal stimulation at high frequency.
4. During apneustic breathing induced by the pontine transection and vagotomy, medullary expiratory discharges were inhibited and inspiratory neurones fired continuously but in a control frequency. The apneusis is just like the inspiratory response to low-frequency vagal stimulation, as far as the changes of respiratory discharges are concerned.
5. Based on these results, two inhibitory systems were proposed in the brainstem, that is, the inspiration- and the expiration-inhibitory system.Neural, organization of the respiratory periodicity was briefly discussed as well.

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During the progressive induction of hypoxia in cats, there occurred small but variable increases in latency of evoked potentials from the retina (ERG), the optic chiasm, the superior colliculus (stratum intermedium) and the visual cerebral cortex. Large and quite variable decreases in the amplitude of these potentials and a simplification of originally complex waveforms occurred along with associated loss of secondary potentials.
Spontaneous electrical activity first was enhanced, then fell off precipitously as the blood oxygen saturation dropped to 30%. After 10 to 15 minutes on reduced inspired oxygen tension, high amplitude spindle-burst activity was observed until the activity became isoelectric. Loss of the slow activity occurred of ter about 10 minutes under hypoxia. During recovery from hypoxia, the slow activity reappeared for a brief time as well as the spindle-burst activity. As the fast spontaneous activity approached the pre-hypoxia amplitude levels, both spindling and slow activity disappeared.
When these results were compared to previous data collected under hypothermic conditions, the effects were quite different. In the case of hypoxia there is a lack of available oxygen at the neural tissue level ; in the case of hypothermia, the neuronal metabolism is reduced by the gradual blocking of intracellular enzyme systems by cold even though adequate oxygen in the blood is available.

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1. In the rabbit, there exist three venae cavae which empty into the right atrium (RA) by separate ostia: the left superior vena cave (LSVC), the right superior vena cava (RSVC), and the inferior vena cava (IVC). Electrical and mechanical responses of the venae cavae proximal to the heart were recorded and compared with those of the atria in vitro, by the aid of microelectrodes and a strain gauge transducer.
2. Spontaneous or electrically driven twitch tension, elicited by an single action potential, could be recorded from each of the superior venae cavae (SVC);however, neither action potential nor contraction was obtained from the IVC.This fact was discussed in relation to the histological findings.
3. The orifice of the SVC contracted 20-30 msec earlier than the RA. This supports a hypothesis that rhythmical contractions of the SVC play a role of a venous valve in preventing blood regurgitation from the RA.
4. Under certain conditions, the LSVC exhibited a tetanus like contraction followed by the contractile summation, and a ‘seeming dissociation’ of E-C coupling. These results may suggest that the SVC have a more fragile intercellular connection than the atria, from the functional point of view.
5. Abrupt changes of stimulus frequency, from a higher (4 cps) to a lower (1 cps) value or vice versa, brought about normal or reverse staircase phenomena in the LSVC as well as in the left atrium (LA). In the LSVC, however, the contractile inhibitory process (fatigue) during normal staircase effect occurred more easily than in the LA.
6. Frequency-tension relationships in the LSVC and the LA were similar to each other on the whole. But the frequency causing the ‘infinitesimal phase ’of contractile force was significantly different from each other, e. g., the LSVC, 20±2.7 cps ; the LA, 43±3.8 cps.
7. Phenomena of rest contraction were recognized in the LSVC as well as in the LA. The rest contraction reached a maximum after 60-200 sec of quiescene in each of them. After the overly long rest-intervals (1000 sec or more), however, the rest potentiation of the LSVC had disappeared more rapidly than that of the LA. That is, the LSVC falls into hypo-dynamic state more rapidly than the LA.
The possible explanations for above-mentioned (5, 6 and 7) differences between the LSVC and the LA were discussed with reference to the calciumsusceptibility of their fiber membranes.
8. In the electrically induced arrhythmias, an arbitrary contraction ‘z ’ had, at first sight, no particular relation to the preceding cycle length ‘y ’ nor the cycle length ‘x’ prior to ‘y’. However, highly positive correlation existed between ‘z’ and ‘y/x’ in each of the LSVC and LA. In these arrhythmias, moreover, the longer the 85%-duration of an action potential and the shorter the 35%-duration, the larger was the contraction ; 60%-duration was nearlyconstant regardless of the marked changes of twitch tension. The wide fluctuation of the strength of twitch tension was discussed with relation to calcium and/or potassium-concentration at the immediate extracellular spaces.
9. In general, the vascular muscle of the SVC proximal to the heart of a rabbit shows a similar nature to the atrial muscle in both electrical activity and contractility. Nevertheless, some difference in their nature was recognized.These differences may depend upon the complexity of the structure of the wall of the proximal SVC which is composed of striated muscle and smooth muscle, or the mixture of the two.
From the above-mentioned results, it seems reasonable to assume that the muscle of the superior venae cavae proximal to the heart has a position between the cardiac striated muscle and the vascular smooth muscle from the functional point of view. Further studies into this problem may be necessary.

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