Twenty five mongrel adult dogs were infused with isotonic HC1 solution (0.6-9.2 mEq/Kg), and the changes of acid-base balance in the blood and the excretion of excessive acid in the urine were observed until the normal acid-base balance in body fluid was restored. Results obtained are outlined as follows: 1. The pH and bicarbonate in the blood decreased in proportion to the acid load at the end of acid infusion, and depression of pH and bicarbonate in the blood of 3 dogs out of 5 which died of the acidosis was over 0.2 pH and 15 mEq/l respectively.
2. The acid infused was neutralized mainly (about 60%) by the extracellular buffer (especially by bicarbonate), and the rest (about 40%) by the intracellular buffer at the end of infusion. After 24 hours, however, the large part of acid load (about 3/4 of the total) was buffered by the intracellular fluid, a part (1/4) was excreted in urine, and thus the alkali reserve in extracellular fluid was completely restored. The excess acid was gradually excreted after a lapse of days mainly as ammonium chloride and partly titratable acid, or inclusively as the base economy. After 2-8 days, the excretion was completed.
Thus the regulation of acid-base balance in body fluid after acid loading was carried out in three steps, i. e. neutralization by extracellular buffer, neutralization by intracellular buffer and renal excretion as the base economy.
3. By measuring the distribution and the amounts of Na, K, Cl and HCO₃ in extracellular fluid, it was confirmed that neutralization by intracellular buffer after acid administration was effected mainly by an alkali shift from the cells in the early period, and by the penetration of the acid radical (Cl) into the cells thereafter.

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1. The inhibtory action of γ-aminobutyric acid (GABA) and of various other ω-amino acids was proved on the crayfish stretch receptor, perfused frog's spinal cord, while α-amino acids related to them were found ineffective.
2. The structure-effect relationship of these inhibitory compounds on the test preparations employed was almost similar: the NH₂ and COOH end groups are essential for the blocking action on the discharge of stretch receptor and the spinal reflex activities as well as for preventing the animals from lethal convulsions and blood pressure lowering, while such effects are most potent when these two end groups are separated by three carbon atoms, lengthening and shortening of carbon chain producing a decrease in their effectiveness. With the same chain length, addition of OH group also reduces the effectiveness, but addition of CH₃ group seems to exert hardly any effect on it.
3. It was also proved on the crayfish stretch receptor and perfused frog's spinal reflexes that ω-amino acids have anti-acetylcholine, anti-serotonine and antinicotine actions, their potency in these actions being parallel with those of their inhibitory actions by themselves. These antiactions as well as their own inhibitory action were antagonized by atropine, tryptamine, lysergic acid diethylamide, dibenamine, picrotoxin and metrazol, but not by pyribenzamine and strychnine.
4. It was found on the frog's spinal reflexes that vitamine B₁ and B₁₂ do not transform the inhibitory action of GABA into an excitatory one, a fact which is not relevant with that reported by Hayashi on dog's generalized seizure.

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1. The two types of electrical activities of the hippocampus evoked by direct stimulation of the brain have been studied in unanesthetized rabbits, immobilized by tubocurarine.
2. The slow wave pattern of the hippocampal electrical activity, characterized by the regular slow waves at 5 to 7 cycles per second, was induced by direct stimulation of the medial preoptic area, medial hypothalamic region, central gray matter and dorso-lateral part of the tegmentum of the midbrain.
3. The fast wave pattern of the hippocampal electrical activity, characterized by low voltage fast waves at 15 to 30 cycles per second, was elicited by direct stimulation of the medial septum, lateral hypothalamus and medio-ventral part of the tegmentum of the midbrain.
4. The slow and fast wave pattern of the hippocampal electrical activity may represent activity of the separate system within the brain, sympathetic and parasympathetic activities.

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Thick, ribbon-like nerve fibers are distributed in the connective tissue surrounding the secretory tubule of the horse sweat gland. They ramify and give rise to fine, tortuous fibers, which form a terminal reticulum on the outer surface of the myoepithelium of the secretory tubule.

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Membrane resting and action potentials of the oyster heart were studied, using both an ultramicroelectrode and a suction electrode. Intracellular action potential and the monophasic extracellular action potential led off from the suction electrode show very similar patterns. Action potential can be classified into two types, but they all have a basic slow potential change superimposed by a rapid spike component. The close similarity of action potential to the vertebrate smooth muscle action potential or the pacemaker potential was discussed. With the application of picrotoxin, remarkable prolongation of action potential resembling the vertebrate cardiac action potential was obtained.

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Effects of a single shock stimulation of the cerebral cortex were examined upon the evoked potential of the thalamic somatosensory relay nucleus (ventrobasal complex) elicited by stimulation of the posterior funiculus at the level of the first cervical segment of the spinal cord. The animals, cats and dogs, were immobilized with tubocurarine or anesthetized lightly with pentobarbital sodium.
1. When recorded monopolarly, the thalamic somatosensory evoked potential was a monophasic positive wave consisting of an initial, high-amplitude, sharp deflection followed by a late discharge of low amplitude.
2. When a single shock stimulation of the somatosensory cortex, ipsilateral to the thalamus explored, was applied preceding posterior funiculus stimulation by time intervals more than about 100 msec, the thalamic evoked potential was suppressed in its initial component and enhanced in its late discharge. Such modification of the thalamic evoked potential lasted with decreasing strength for several hundred msec. after cortical stimulation.
3. The cortical points of the somatosensory area which were capable of exerting the most manifest effect upon the thalamic evoked potential coincided with those most strongly activated by the thalamocortical projection system.
4. Evoked potentials recorded from the medial lemniscus upon posterior funiculus stimulation suffered no detectable influences by electrostimulation of the somatosensory cortex.
5. By recording spike discharges from the thalamic somatosensory relay nucleus with the use of fine electrodes, effects of electrostimulation of the somatosensory cortex were examined upon them. When a peripheral stimulus was preceded by a cortical stimulus at about the same time intervals as in the observations with gross electrodes, there occurred a conspicuous increase in the number of spike discharges in response to peripheral stimulation.
6. After an entire extent of the somatosensory cortex was aspirated acutely, the thalamic evoked potential was augmented in the initial component with the late one suppressed. This effect was strictly confined within the thalamus ipsilateral to the cortex extirpated.

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The mechanism of the crossing of the i-t curves of M wave and H wave has been investigated in 85 decerebrated adult cats.
M wave and H wave were picked up from the gastrocnemius and soleus muscles. Antidromic ventral root impulses (AMI), dorsal root inflow (DRI) and monosynaptic reflex (MSR) were picked up from cut ends of the Si or L7 spinal root. As a rule, percutaneous stimulation was delivered to the tibial nerve.
1. The i-t curves of M and H waves frequently crossed each other in the cat as in man.
2. No crossing of the i-t curves of AMI and DRI was observed; the threshold of DRI was lower than that of AMI at any duration of stimulation, that is to say, the threshold of the group Ia fibers was always lower than that of the motor fibers in the tibial nerve.
3. Crossing was observed between the i-t curves of AMI and MSR. On the basis of this result and of the theoretical consideration, the problem concerning the crossing of the i-t curves of M wave and H wave was reasonably converted to that of the i-t curves of AMI and MSR.
4. The crossing of the i-t curves of AMI and MSR was found to be brought about by the following two phenomena, central and peripheral: A certain magnitude of DRI was needed to produce the threshold MSR. In this case, not the amplitude but the area of DRI was constant irrespective of the duration of stimulation.
Crossing was observed between the i-t curve of AMI and the iso-area curve of DRI, i. e., the i-t curve giving constant area of DRI.
5. The phenomenon stated in 4, (b) was observed in the case of percutaneous stimulation of the tibial nerve but not in the case of direct stimulation. This difference was verified not to be due to the wave form of stimulation distorted by the polarization of the skin but to the indirect stimulation through volume conductors.

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The periodic contraction in the isolated lung of the Japanese toad was observed and the necessary condition for its occurrence was analyzed.
The periodic contraction is apt to occur in summer rather than in winter, and its rhythm is about 10-20/hour in summer and about 4-12/hour in winter.
The temperature coefficient of the rhythm is 2.3 in average and shows no seasonal variation, The rhythm and size of the periodic contraction are hardly influenced by such drugs, as autonomomimetic, autonomic blocking, anesthetic agents etc., but markedly by the change of the ionic environment or the muscle stretch.
The periodic activity is myogenic in origin, and its development may closely be related to the ionic condition.
The periodic contraction may be regarded as a rather non-physiological contraction provoked by changes in environmental conditions, which result inevitably from the isolation of the lung and other experimental procedures.

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The intestinal intrinsic reflexes are comparatively studied using the small intestine in situ as well as in vitro of dogs, rabbits and guinea pigs.
1. When the contraction waves propagate along the wall of the small intestine in situ, the effect of the mucosal intrinsic reflex generally consists of the reinforcement of the waves above and their weakening below the spot stimulated. This effect occasionally can be mixed with that described in 2.
2. When the propagating waves are hardly seen in the small intestine in situ, as is the case in guinea pigs, there occurs just above the spot stimulated a rise in tone superimposed by pulsations which send out the waves, the one travelling orad, whereas the other travelling anad but inhibited in its course.
3. In dogs and rabbits stretching the wall of the small intestine in situ produces usually an extracontraction followed by the inhibition of motility both above and below the stimulated spot. In guinea pigs the same stimulus as above initiates easily a series of extracontractions, while an inhibition, which may be expected to follow them, is not conspicuous.
4. In the small intestine in vitro the effect of the intrinsic reflexes are abolished completely in a short time (about 30 minutes.) after its isolation. However, the extracontractions produced by stretching the intestinal wall are fairly strong. From the results described above it may be concluded that the so-called reflex peristalsis, observed in guinea-pig small intestine in vitro, is not neurogenic but myogenic in its nature.

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The effects of inhibition of the aerobic glycolysis by sodium fluoride and inhibition of respiration by sodium fluoroacetate on the carbohydrate metabolism and cardiac function were investigated on the isolated bullfrog's heart perfused with the heparinized blood.
0.005 M. fluoride did not show any inhibitory effect but an inotropic effect. 0.01-0.02 M. fluoride induced the inhibition of aerobic glycolysis, i. e., the definite elevation of the blood pyruvate level at the end of 2 hours perfusion, the increase of oxygen consumption and the decrease of glucose uptake, and simultaneously the decrease of cardiac output due to the restriction of diastolic relaxation. The same mechanism is suggested on the inhibition of glycolysis and the restriction of diastolic relaxation as Mg-fluoro-phosphate formation inside the cell, while the inotropic effect in the lower concentration may be due to the effect of calcium fixation on the cell membrane in the form of calcium fluoride as Loewi expected.
0.001-0.01 M. fluoroacetate diminished significantly the oxygen consumption with the elevation of blood lactate and pyruvate level at the end of 2 hours perfusion and the augmentation of glucose uptake, while no diminution of the cardiac output. However, when the initial oxygen consumption is close to the level of the warm blooded animal by elevation of the environmental temperature and the heart rate, the cardiac output falls down simultaneously with the depression of the oxygen consumption. It is concluded that the glycolysis is sufficient enough for supplying the energy for the ordinary cardiac function but not enough for the excessive energy demand.

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