1) The electrical properties of the membrane were investigated in the rabbit atrial muscle fiber by using two microelectrodes for recording the transmembrane potential and for current application.
2) The current-voltage relationship of the rabbit atrial muscle fiber in sodium-free solutions was found to be similar to that of the Purkinje fiber, showing an increase in resistance with depolarization.
3) Polarization resistance during activity shortly after the peak of the action potential was lower than in the resting state and gradually increased during the plateau. However, a value higher than that in the resting state was never observed during the plateau phase.
4) The polarization resistances at the peak and during the plateau of the action potential were somewhat larger in the action potentials with higher plateaus than those in the action potentials with lower plateaus.
5) The ionic mechanism responsible for the production of the rabbit atrial action potential is discussed.

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The effects of noradrenaline and isoprenaline on the electrical and mechanical properties of depolarized smooth muscle of the guinea pig taenia coli were investigated by the double sucrose gap method.
1. Noradrenaline (10^-7-10^-5g/ml) decreased the membrane resistance at any given concentration of excess K ion. When increased K ion concentration accelerated the spike discharges, noradrenaline blocked the spike generation as a result of the consequent reduction in membrane resistance, thus causing relaxation. When the excess K ion depolarized the muscle and no spike generation was observed due to depolarization block, noradrenaline no longer caused relaxation of the tissue. Phentolamine (10^-5g/ml) completely blocked the effect of noradrenaline.
2. Acetylcholine (10^-5g/ml) and noradrenaline (10^-5g/ml) reduced the membrane resistance and blocked the spike generation to the same extent in 59 mm K-Krebs solution. However, acetylcholine enhanced and noradrenaline reduced the contraction.
3. Isoprenaline (10^-7-10^-5g/ml) reduced the tonic response of the contraction without any marked changes in the membrane resistance, membrane potential and membrane activity, at any given concentration of excess K ion.
4. Isoprenaline (10^-7-10^-5g/ml) did not reduce the tonic response evoked by excess K ion in Na-free solution. It is suggested that external Na ion might be important for the reduction of the internal free Ca ion concentration. In the Cl-deficient (C₆H₅S0O₃), excess K⁺ condition, isoprenaline again had no effect on the depolarized muscle.
5. When Ca ion in the excess K-Krebs solution was replaced by Sr and Ba ions, the effect of isoprenaline on the tonic response was markedly suppressed.
6. Ouabain (10^-5-10^-4g/ml) reduced the membrane resistance and the tonic response evoked by excess K⁺ (below 59 mm) solution. In more than 59 mm of K ion, ouabain did not cause the tissue to relax. Isoprenaline (10^-7-10^-6g/ml) reduced the tonic response evoked by any concentration of excess K ion in the presence or absence of ouabain.
7. In a concentration of 10^-5g/ml, DNP reduced the membrane resistance and caused the tissue to relax. Isoprenaline (10^-6-10^-5g/ml) also effected relaxation of the tissue during treatment with DNP, although the degree of relaxation was less than without DNP. In 2×10^-5g/mlDNP, the tissue was completely relaxed, and isoprenaline (10^-6-10^-5g/ml) had no further effect on the tone.
8. The possible actions of noradrenaline and isoprenaline on the depolarized muscle are discussed in relation to those on other smooth muscles.

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1. The reabsorptive function of salivation at the duct system of the dog's submaxillary gland was studied in this experiment, where control salivation was initiated by stimulation of the chorda tympani, and experimental salivation was initiated by simultaneous stimulation of the perivascular nerve and the chorda tympani.
2. Osmotic concentration of the experimental saliva was relatively higher than that of the control saliva. The causal factors in the relative rise of saliva osmolality were analyzed by estimation of salt reabsorption and the increment of water permeability at the duct system.
3. Reabsorption of ²²Na at the duct system was measured as an index of the reabsorptive rate of salt. The reabsorption of ²²Na was not affected by stimulation of the chorda tympani and was assumed to be a constant value under this experimental condition.
4. The reabsorptive rate of ²²Na was decreased to 60-75% of the control by stimulation of the perivascular nerve.
5. It was found theoretically that the relationship between the flow rate of saliva (V) and the ratio of osmotic concentration of saliva to plasma (S_osm/P_osm) can be explained by the relation found in a rectangular hyperbolic curve.
6. From the hyperbolic curves which were fitted by inspection to the plots from the actual measurements it was demonstrated that, in experimental salivation, the reabsorptive rate of salt decreased to 60% of the control, the osmotic permeability for water increased to 140%, and the hydrostatic permeability for water increased to 250% at the duct system of the submaxillary gland.
7. Thus the increase of salt concentration in experimental saliva is concluded to be initiated by a decreased osmotic tonicity of fluid reabsorbed through the duct.

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1) The effects of the local anesthetic, quatacaine, on the sartorius muscle fibers of frog have been investigated using an intracellular recording technique, in order to compare them with those of procaine and tetrodotoxine (TTX).
2) Quatacaine increased the electrical threshold of the muscle fiber membrane and reduced or abolished the action potential without affecting the resting potential. These effects of quatacaine were dose-dependent and they were affected by the concentration of sodium in the external solution.
3) Quatacaine and procaine (0.06%) inhibited slightly the delayed recovery and increased the “input” resistance while TTX (10^-7g/ml) had no effect.
4) When the observed membrane constants were used in calculating the maximum sodium conductance (g_Na), g_Na decreased from 19.5 to 6.1 mmho/cm² after the addition of quatacaine (0.03%).
5) It was concluded that quatacaine affects the muscle membrane by diminishing greatly the selective sodium conductance in the active membrane and by reducing slightly the potassium conductance simultaneously in both the resting and active membranes.

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Under light ether anesthesia, the pons was explored with tetanic stimuli to produce or modify rhythmic swallowing in rabbits. The effects of various surgical and pharmacological procedures upon the responses and the topography of the brain stem area concerned were studied.
1) Stimulation of the appropriate area in the pons yielded prolonged repetitive swallowing. The number of swallows that occurred during stimulation was maximum at a certain stimulus intensity (ca. 5 volts) and declined with use of greater intensity. During stimulation above 8 volts no swallowing could be seen. However, the number of swallows occurring after cessation of stimulation was increased by higher stimulus intensities.
2) The pontine area concerned was delimited bilaterally in the reticular formation dorsolateral to the superior olivary nucleus and ventral to the motor trigeminal nucleus.
3) Simultaneous stimulation of the anterolateral frontal cortex greatly enhanced the repetition of swallowing occurring from pontine stimulation.
4) The swallowing response diminished markedly after supracollicular decerebration or restricted bilateral ablation of the frontal cortical area. It was also reversibly suppressed by topical surface application of GABA or Xylocaine or local cooling of the frontal cortex.
5) Pontine stimulation also produced rhythmic chewing and salivation as well as swallowing. However, cortical influences on chewing were greater than on swallowing.
6) Slight facilitation (when pontine stimulation did not exceed 5 volts) and powerful inhibition (at higher intensities) were effected for swallowing elicited by either stimulation of the superior laryngeal nerve or water in the oropharynx.
7) Destruction of the relevant pontine area by electrocoagulation or separation by surgical transection at the ponto-medullary border caused no essential alteration of the elicitation or performance of reflex swallowing.
8) On the basis of these findings and those previously obtained, an intricate neural arrangement connecting cerebral cortex, brain stem reticular formation, medullary integrative center, and afferents from oropharynx for the control of swallowing is schematized and its mode of operation is discussed.

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1) The membrane potentials, currents, and contractile responses were measured in the bullfrog ventricular trabeculae under voltage clamped conditions by means of the double glycerol-gap technique, and the membrane currents responsible for initiation of contraction and relaxation were studied.
2) For the initiation of twitch contraction, the fast Na current was found to play a minor role, producing less than 6% of the maximum tension, whereas the slow current system was most important.
3) Under constant presence of tetrodotoxin (10^-7g/ml), 50% Na-depletion produced a marked augmentation of the active slow inward current as well as contractile tension and a conspicuous decrease in the threshold voltages, indicating the presence of Ca-Na antagonism in this slow current system. These effects, however, became temporary when external Na concentration was further decreased to 25% or totally eliminated.
4) Na depletion experiments also revealed that a steady outward current due to elimination of leaky Na inward current was accompanied by a sustained tonic contracture, while reintroduction of Na ions elicited a steady inward current and a relaxation of contracture.
5) Kinetics of tension development due to rectangular depolarization and relaxation due to repolarization appeared quite different, the former showing a complication and the latter a simple exponential curve in Nadeficient condition. Na ions accelerated the relaxation by decreasing the time constant and appeared necessary for rapid relaxation.
6) These results suggest a presence of more than two types of excitationcontraction systems in the bullfrog ventricle; the fast and slow inward currents responsible for the initiation of phasic contraction and some Na-Ca exchange mechanism responsible for that of tonic contraction and for the relaxation of phasic and tonic contractions.

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1) Properties of the slow potential changes recorded from antral and pyloric regions of the guinea pig stomach were investigated with both the double sucrose gap and microelectrode methods.
2) Frequency, amplitude, and duration of the slow potential changes varied from 2 to 5 per min, 0 to 30mV, and 6 to 14 sec.
3) During the slow potentials, membrane resistance was reduced. This reduction exceeded that caused by the rectifying property of the membrane.
4) The amplitude of the slow potential was enhanced by application of weak inward current pulses and decreased during weak outward current pulses.
5) The frequency of the slow potential changes was a function of the temperature. The Q₁₀ value was 3.2.
6) Na-deficient (1/10 Na) Krebs solution suppressed the slow potential changes, but they were restored by conditioning hyperpolarization of the membrane. However, in Na-free solution the slow potential changes were generated with neither normal nor hyperpolarized membrane.
7) In low K- and low Ca-Krebs solutions, the amplitude and frequency of the slow potential changes were reduced.
8) When Cl ion was replaced by the less permeable C₆H₅SO₃ ion, the slow potential change was abolished completely. When. Cl ion was substituted with Br ion, the frequency of the slow potential was not reduced, and in some preparations it was increased.
9) Ba ion in the presence of Ca ion increased the frequency of the slow potential changes, but in the absence of Ca ion the frequency was not increased. Sr ion could not be substituted for Ca ion in the generation of the slow potential changes.
10) Prostigmin (10^-6g/ml), atropine (10^-6g/ml), and tetrodotoxin (10^-6g/ml) modified the frequency of the slow potential changes. However, the effects of these drugs were inconsistent.
11) Acetylcholine (10^-7g/ml) increased the frequency of the slow potential changes. At a concentration of 10^-6g/ml, acetylcholine depolarized the membrane to a level above the peak of the slow potential changes. Conditioning polarization of the membrane in steps proportionally enlarged the amplitude of the depolarizations in steps.
12) Catecholamines (noradrenaline and isoprenaline) suppressed the generation of the slow potential changes. Noradrenaline (10^-6g/ml) increased the membrane potential, reduced the membrane resistance, and abolished the slow potential changes. Isoprenaline (10^-6 g/ml) only slightly hyperpolarized the membrane and did not reduce the membrane resistance. The effect of noradrenaline was almost completely blocked by phentolamine (10^-6g/ml).

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