Electrical activity of lobster cardiac ganglion was studied by intracellular recording when the trunk had been partially treated with high Ca or high K solution. Special attention was paid to the functional relation between ganglion cells. Activity of the posterior half of the ganglion trunk was mainly represented by that of the fifth large cell.
1. When the Ca was applied to the four large cells in the anterior part of the trunk, their activity was depressed completely, but often slow potentials and trains of synaptic potentials induced by intact cells remained.
2. When the Ca bathed the posterior half of the trunk, the activity of anterior four large cells was sometimes depressed completely, or some components of the burst remined.
3. When the K was applied to the anterior part of the trunk, periodic burst was still observable in the group of anterior four large cells and hardly had a relation to impinging synaptic potentials.
4. Periodic burst was found as before in the four large cells with frequent occurrence of trains of small synaptic potentials even after the K was applied to the posterior part of the trunk.
5. In preparations producing periodic burst in the group of large cells, the burst activity was sometimes depressed completely or inhibited remarkably when the Ca was applied to either half of the trunk. On the contrary, interval and duration of the burst were shortened when the K was applied to either half of the preparation.
6. Ca solution produced an inhibitory effect on the intact cells as the result of electrotonic spread of hyperpolarization manifested in the applied half of the trunk.

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1. A study was carried out of the effect of caffeine and low temperature on smooth muscle of the toad bladder.
2. Spontaneous rhythmic contraction of smooth muscle is suppressed by the action of caffeine.
3. Rapid cooling elicits muscle contraction. Although spontaneous rhythmic contraction of the smooth muscle disappears with the application of caffeine, contraction is elicited by a rapid cooling treatment.
4. Unlike skeletal muscle, smooth muscle does not contract with upon repeated rapid cooling.
5. When caffeinized muscle, immersed in Ringer's solution, of which part of the sodium has been replaced with an equivalent amount of sucrose, is subjected to rapid cooling, the tension of the muscle increases in proportion to the amount substituted.

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The threshold depolarization in frog sartorius muscle fiber was relatively constant when stimulated with moderate pulse duration (1-10 msec). With shorter or longer pulse duration, the threshold depolarization increased. The pulse energy in the energy curve (i²t-t) obtained. from strength-duration relationships had a minimum value at approximately 1/4 of the combined time constant of the fiber membrane. The “apparent” input resistance was minimum with a stimulus whose duration was 1/4 of the combined membrane time constant. The maximum local response or subthreshold response reached the same amplitude regardless of the stimulus duration and reached its peak after the termination of the stimulus current. The time course of its development was slower, with a longer pulse duration. The safety factor calculated from maximal subthreshold response was approximately 8.
The results obtained indicate that the frog sartorius muscle fiber has an optimal duration for square wave stimulation of approximately 1/4 of the combined membrane time constant of the fiber, and that sodium conductivity of the membrane during application of the square wave pulse seems to be largest at this moment.

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The visually evoked cortical responses we recorded in the light-adapted state consisted of primary complexes and spike-like waves. The properties of the latter waves, which we have called the light-adapted response (LAR), were studied at several levels of light adaptation.
1) The amplitude and latency of the LAR varied systematically depending upon the ratio between the intensities of photic stimulus and adapting light.
2) The LARs were classified into two groups: early and late L-waves. The early L-waves (L1-L3), which had a variable crest time, were produced predominantly at the higher level of light adaptation, whereas the late L-waves (L4-L6) with fixed crest time were produced at the lower level of adaptation.
3) When the intensity of the adapting light was increased nearly to that of the test flash, the critical LARs were recorded accompanying the suppressed primary complexes. The time interval from the primary complex to the critical LAR remained constant, regardless of stimulus intensity. At the same ratio of adapting light to stimulus, a similarity in wave-form and amplitude of the critical LAR was found. Within the intermediate range of stimulus light, the threshold (log I) of the cortical LAR increased proportionally with the increase in level of light adaptation (log L) after Weber's law. The critical contrast index calculated for this log I-log L curve was about-1.5.
4) In human subjects, brightness discrimination curves were also determined by the same photic apparatus used for the animal experiments. The results indicated that the brightness discrimination curves (log T-log B curves) which were obtained with a test field of 20° in visual angle showed a linear relationship following Weber's law. This log T-log B curve coincided with the log I-log L curve obtained in animals. The contrast index calculated for this log T-log B curve was about-1.5 to-1.8.
5) This agreement between electrophysiological and psychophysical findings suggests a close relationship between subjective liminal brightness discrimination and the critical LAR of the cortical response.

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Transmembrane potentials of the ventricle of the isolated chicken embryo heart were recorded by a microelectrode technique. Substitution of foreign anions for chloride depressed the aconitine-induced rapid firing of the specimens. The effectiveness of anions in depressing the rapid firing was in the order of thiocyanate, iodide, nitrate, bromide, and then acetate. Alteration in chloride permeability participates in the process of the arrhythmias, and foreign anions can affect the arrhythmias.

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By using the single sucrose-gap polarization method the relation between membrane potential and contractile tension was analyzed in the frog toe muscle. Two-phase sustained contraction was produced by a prolonged, relatively strong depolarizing pulse. The first phase developed and was inactivated rapidly, while the second phase developed slowly and was maintained during depolarization. Tetrodotoxin in 10^-6g/m1 did not suppress either phase of contraction. When the transverse tubules were disrupted by hypertonic glycerol treatment, the sustained contraction was completely abolished. The prolonged hyperpolarizing pulse which was applied shortly before the depolarizing pulse exhibited a marked inhibitory effect on the sustained contraction, especially in the first phase, without causing any noticeable change in the depolarization level. The inhibitory effect depended on the interval between hyperpolarizing and depolarizing pulses and lasted more than 1 min. The nature of the effect of hyperpolarization was analyzed. The well-known suppressing effect of the preceding hyperpolarization on the “creep” phenomenon was confirmed in the toe muscle fibers. It was concluded that hyperpolarization has some direct effect on the excitation-contraction coupling process, especially on the transverse tubular system and the sarcoplasmic reticulum.

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Electrical and mechanical properties of M. digastricus of the guinea pig were investigated by the microelectrode and strain gauge methods.
1) The mean diameter of the musclefibres was 45.9μ. The triad structures appeared in the region of the A-I junction, i. e. two triad structures appeared within one sarcomere.
2) The resting membrane potential was-81.9mV. One type of muscle fiber had a length constant 0.72 mm, specific membrane resistance 1, 300Ωcm², internal resistance of the muscle 290Ωcm, whereas the other type of muscle fiber gave values of 0.72mm, 330Ωcm² and 73Ωcm respectively.
3) The changes of the membrane potential in various external concentrations of K ion were observed. The maximum slope of membrane potential change for tenfold change of K ion was 54 mV in solutions prepared so that [K] _o×[Cl] _o=constant.
4) Spikes could be elicited by electrical stimulation. The overshoot was 15 mV and the maximum rates of rise and fall were 340V/sec and 134 V/sec respectively.
5) The conduction velocity of excitation was 2.9m/sec, the time constant of foot of the propagated spike was 0.1 msec and the chronaxie was 0.39 msec.
6) The time constant of the membrane was calculated by various methods based on the cable theory, and the calculated values of the time constant were discussed in terms of the activity and structure of the muscle.
7) Although two types of the muscle fibre were distinguishable from their electrical properties, these two types could not be classified, from the results of this study, into fast and slow (or twitch and tonic) muscles.
8) Electrical stimulation and excess K ion evoked tension development, the threshold potential necessary to produce tension development being-35mV.
9) Caffeine and thymol modified the mechanical responses of the muscle. Caffeine enhanced the amplitude and prolonged the time taken to reach the peak of the contraction. Thymol, on the other hand, prolonged the relaxation time. Presumably caffeine increased the release of Ca ion and thymol inhibited the reabsorption of Ca ion by the reticulum.
10) The mechanical responses of M. digastricus were compared with those of M. semitendinosus.

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1. Effects of caffeine on the electrical and mechanical properties of the atrial muscle of guinea pig were investigated.
2. In normal Krebs solution, 3mM caffeine caused a more than 5-fold potentiation of contraction. The potentiation, however, became smaller the higher the concentration, and 50mM caffeine depressed the contraction somewhat in its later phase.
3. In 3mM caffeine, the duration of action potential was prolonged up to 140% at a height of 80% of the spike, and in 50mM caffeine, up to 230%, whereas the membrane slope resistance was decreased. The rate of rise of the action potential appeared enhanced at the later phase.
4. In sodium-free Tris-maleate Krebs solution, even 3mM caffeine evoked a contracture, and the contracture tension tended to increase with concentration of caffeine.
5. By soaking the muscle in low calcium Tris-maleate Krebs solution the amplitude of caffeine contracture decreased, first rapidly and then slowly with time, suggesting the contributions of surface membrane and internal calcium store towards contractile activation.
6. These results are interpreted as indicating that:
a) Caffeine acts on both the surface membrane and the sarcoplasmic reticulum in the myocardium.
b) Enhancing the inward calcium movement, caffeine augments the contraction both directly and indirectly through the sarcoplasmic reticulum.
c) In normal Krebs solution, the amount of the accumulated calcium is small but is increased by sodium depletion.

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