A new extended membrane equation applicable to carriermediated active transport is derived, as follows:
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where ΔE is membrane potential, ψ and Φ correspond to active-transport flux and carrier-mediated flux respectively, and other notations have their usual meanings in membrane equations.
By means of electronic data processing, such an extended membrane equation is applicable to computation of the ion permeability coefficients of the skin of frog, toad, and newt using a least-square method. Applying the two-membrane theory of Ussing, the membrane potential of the amphibian skin is obtained as follows:
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and
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These relations show a fairly good respective agreement with the observed potentials. Application of such an extended equation not only avoids the appearance of a physiologically meaningless negative permeability coefficient for some one of the ions, as is often obtained by applying the original Goldman equation, but also results in a fairly reasonable value for these coefficients.

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Alveolar carbon dioxide pressure-ventilation response curves were measured on 5-6 consecutive days by the rebreathing method of Campbell and his associates. The slopes of the response curves progressively increased until the third day and then leveled off. The ventilatory response evaluated by breath-by-breath recording after a single large breath of hypercapnic and/or hypoxic test gases also increased in the same manner when studied at the same time. This phenomenon was thought to be related to the altered neurogenic activity in the ventilatory control system. The slope of the response curve obtained by the conventional steady state method did not show the consistent increase observed with the rebreathing method.

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1. Mechanisms of occurrence of the fibrillation induced in the toad's heart by excess calcium in Ringer's solution were studied by measuring the threshold current, the conduction velocity, the absolute refractory period and the transmembrane potential.
2. In the ventricle, excess calcium in Ringer's solution elevated the threshold current, slowed the conduction velocity and shortened the absolute refractory period. When the height of the action potential was reduced, the maximum rate of depolarization decreased and the duration of the action potential shortened without altering the level of the resting potential. At about 7 times the normal [Ca]_o, fibrillation occurred in response to a single stimulus.
3. Sodium or potassium deficiency in Ringer's solution potentiated the cardiac effect of excess calcium and facilitated the occurrence of fibrillation. On the contrary, excess potassium in the perfusing fluid antagonized it.
4. These results were interpreted as indicating that:(a) Effects of excess calcium on the cardiac excitability are caused by the suppression of sodium permeability of the membrane during excitation, and (b) The mechanism of fibrillation might be due to a reentry of excitation.
5. The atrium required much higher [Ca]_o (about 10 times the normal value) for an induction of fibrillation. Application of acetylcholine or potassium deficiency in Ringer's solution facilitated an induction of fibrillation. Difficulty to induce fibrillation in the atrium only by excess calcium indicates the relatively lower sensitivity to excess calcium than in the ventricle. In addition, slight prolongation of the absolute refractory period by excess calcium was observed in the atrium. The fact that the atrial tissue contains more calcium but less potassium than the ventricular ones suggests the different sensitivity to excess calcium between them.

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The stimulating effect of NaCl added to HCl solution upon the palatal chemoreceptors of the carp was studied by recording the responses from the palatine nerve innervating the palatal organ.
In summated multifiber responses, the addition of NaCl at relatively weak concentrations enhanced the effect of HCl solutions. The effect of NaCl of a fixed concentration varied with varying concentrations of HCl, yielding a shift of the response-HCl concentration curve toward a lower concentration range. The enhancing effect of NaCl depended also on its own concentration. The response at a fixed HCl concentration increased as the concentration of NaCl was raised. At high concentrations of NaCl, however, the response did not increase with a rise in the concentration of NaCl in spite of the fact that a rapid increase of the response to plain NaCl solutions was observed at that concentration range.
Some fibers were found that did not respond to NaCl but responded to mixtures of NaCl and HCl with higher impulse frequencies than to acid solutions alone. Other fibers, though responding well to NaCl, showed only a poor response to mixtures of NaCl and HCl. These fibers did not respond at all to plain acid solutions.
The effects of NaBr, NaClO₄, NaI, NaNO₃, NaSCN, Na₂SO₄, KCl, LiCl, NH₄Cl, RbCl, choline chloride, CaCl₂, MgCl₂, and MgSO₄ added to HCl solutions on the summated response were also studied. All of these salts except MgSO₄ and Na₂SO₄ enhanced the response to HCl about equally. The sulphate appeared to have a depressant effect.
These results suggest that the enhancement of the response to HCl by NaCl and other salts may be related to the activity of the acid receptor rather than the salt receptor. In addition, the results with NaCl suggest the presence of salt receptors whose responses to NaCl are depressed in the presence of HCl or at a low pH.
The stimulating effects of H₂SO₄, HCl, and HNO₃ were compared by recording the responses from multifiber strands: H₂SO₄ was found to be less effective than the other two monobasic acids over the pH range used.

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1. Electro-mechanical coupling in the crayfish short muscle fibers was investigated by the voltage clamp method using intracellular microelectrodes.
2. The change in membrane potential was uniformly distributed when depolarization was more negative than -20mV and longer than 100 msec.
3. The mechanical threshold potential was -50 to -58mV. The curve relating the tension to the membrane potential was nearly linear in the range between -45 and -20mV for every duration of depolarization. The slope of the curve was 0.3 of the tension at 0mV for 10mV change in potential. The tension-membrane potential curve obtained in the potassium contracture experiments was quite similar to that in the voltage clamp experiments.
4. The rising phase of isometric contraction, except for the initial phase within 0.1 sec, was explained by two exponential components. The time constants were 0.4-0.6 sec and 0.08-0.12 sec at 20-25°C, and they were independent of the membrane potential.
5. The relaxation phase after the end of depolarization was also explained by three exponential components. The time constants were 0.4-0.65 sec, 0.10-0.12 sec, and 0.05-0.08 sec at 20-27°C, and they were independent of the level and duration of the clamped membrane potential.
6. The mechanical threshold potential was unaffected by the change in the speed of depolarization. The maximum rate of tension rise did not decrease until the speed of depolarization was reduced to the critical value of 40-80 mV/sec.

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1. The effects of divalent metal ions on electro-mechanical coupling were examined in crayfish muscle fibers, using the voltage clamp method. Metal ions were added by substitution for Na. The relation between tension and membrane potential was directly figured by leading tension and potential to the Y and X axes of the oscilloscope and by depolarizing the membrane very slowly with the linearly rising pulse.
2. Replacement of NaCl with equimolar choline chloride shifted the tension-membrane potential relation toward a more negative potential.
3. Divalent metal ions elevated the mechanical threshold potential and decreased the tension at the given membrane potential. They not only shifted the curve relating tension and membrane potential along the potential axis but also decreased the slope of the curve. The order of the inhibitory action was Cd>Co≥Mn>Ni>Ca≥Mg>Sr>Ba. Their inhibitory effects appeared fairly rapidly after addition of metal ions and disappeared, fully reversibly, after their removal.
4. The time courses of tension rise after the start of depolarization and its fall after the end of depolarization were explained as the sum of two or three exponential components. The time constants were not changed by metal ions.
5. Caffeine lowered the mechanical threshold potential and shifted the tension-membrane potential relation toward a more negative potential.
6. It is suggested that the inhibitory effect of metal ions on tension results from their stabilizing action on the Ca-permeability of the internal membrane system.

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The lateral-line organ of Xenopus laevis was studied by recording responses from its afferent nerve fiber. The firing rate was registered with the aid of an electronic rate meter.
1. The firing rate was remarkably increased by stimulation with KCl and NH₄Cl.
2. Sodium salts (except for Na-glutamate) suppressed both the spontaneous activity and responses to other cations. Na-glutamate did not show the suppressive effect at all.
3. Salts of divalent cations, CaCl₂, and MgCl₂, increased the firing rate, in contrast to the results obtained with fish, where they suppressed the responses to monovalent cations.
4. The discharge pattern from all the afferent fibers examined was quite uniform, so that the fibers could not be separated by response patterns into different groups.
5. Neither tetrodotoxin nor Mn⁺⁺ suppressed the responses to solutions of salts, including those of Ca⁺⁺.
6. Sucrose and quinine produced no remarkable effects, in contrast to the effects produced on the gustatory organs.
7. Dihydrostreptomycin sulfate (SM) suppressed both mechano- and chemoreception.
8. Along with serving as a mechanoreceptor, the lateral-line organ of Xenopus probably functions as an external chemosensory organ in detecting ions in the environment.

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The load-velocity relations were determined at various contractile forces in the small bundle dissected from frog semitendinosus muscle.
1) The tension-extension curve of the bundle was nearly the same as that of single fibers.
2) The load-velocity curves of shortening muscle obtained at the standard length L₀ fit HILL'S hyperbolic equation at any contractile force in the partially activated muscle, and the dynamic constants were a/P₀=0.25 and b/L₀=0.9/sec at 10°C. The viscous-like force F_v at a given velocity increased linearly with increasing contractile force F. These results were valid in the length region between 0.8 and 1.2 L₀.
3) The load-velocity curves of lengthening muscle were also hyperbolic at any contractile force and F_v was also proportional to F, unless the velocity exceeded 1.0 L₀/sec. The dynamic constants were a'/P₀=0.4 and b'/L₀=0.85 /sec, i. e., a'/P₀ was 1.6 times larger than a/P₀.
4) HILL's force-velocity equation was generalized to the force (F)-load (P)-velocity (v) equation (P+A)(v+b)=b (F+A), A=aF/P₀; or the force-Fv-velocity equation Fv=(F/P₀)(P₀+a) v/(v+b).
5) The value of F_v on lengthening was 1.4 times larger than that on shortening under the same contractile force and velocity.
6) These force-load-velocity equations were valid not only during steady contractile force but also for any instance during the change in contractile force.
7) The significance of F_v, or force-dependent viscosity, is discussed with respect to the sliding filament theory.

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