Many theories have been proposed on the genesis of respiratory sinus arrhythmia (R.S.A.).
The authors have examined a model of the arrhythmia in which haemodynamic disturbance upon a closed loop pressure regulator is assumed to be one of the most important cause under the clinical status.
At first, a model of the blood pressure regulator was constructed and examined deliberately. As the result, it has been revealed that the system has double controlling mechanism, which composes a blood pressure setting loop controlling parametrically the arterial resistance as well as the vagal efferent tone and a pressure regulating loop performing equivalently a negative feedback due to the vagal control of the sino-atrial node.
Then, being forced by an assumed blood pressure disturbance due to respiration, this pressure regulating system was tested by transient as well as frequency responses. The data obtained in men and the model have shown good agreement each other.
Finally, manipulating the arterial resistance and/or the central vagal tone, the we have studied the parametric controllability of the model, and obtained quite interesting results. For instance, according to the increase of the vagal tone, the average heart rate becomes slower, and the R. S. A. becomes more distinguished. These facts may well explain the clinical features in men with hypertonus of the vagus, and seem to tell us the plausibility of this model.

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In an automatic interpretation of electrocardiogram (ECG) by a digital computer, it is important to recognize the irregularity of rhythms and to read the waveforms of one particular cycle.
This paper deals with an automatic pattern recognition of the ECG rhythms based oz1 processing of 150 samples of clinical ECGs, each consisting of a series of 127 successive RR time intervals. There are many kinds of patterns of ECG rhythms, but in this paper, compensatory extrasystole, non-compensatory extrasystole, interpolated extrasystole, block, respiratory arrhythmia, bigeminy, trigeminy, polygeminy, Wenckebach's period, and several others were taken as fundamental types of rhythms. For the automatic recognition of these patterns of rhythms by a digital computer, firstly, quantitative definition of each pattern was given and then a special classification logic was constructed by means of deterministic, not by stochastic approach.
The results of computation indicate that the quantitative evalutation of rhythm as described in this paper provides a useful basis for the computer diagnosis of heart disease as well as of arrhythmia.

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A new method has been developed for continuous determination of pCO₂ of blood in vivo. When the carrier, pure water, is in contact with the sample solution containing carbon dioxide through a semipermeable membrane, the carbon dioxide will pass to the carrier at a rate proportional to the partial pressure. If the carrier is flowing at a constant mass flow rate, the carbon dioxide density of the carrier is proportional to the pCO₂ of the sample. Thus, all we have to do is to measure the carbon dioxide density of the carrier in order to know the pCO₂ of the sample. Instead of the direct measurement of the density, we determined the electric conductivity variation of the carrier which was caused by the carbon dioxide passed through the membrane from the sample.
Satisfactory results were obtained in continuous determination of pCO₂ of sample solutions containing different electrolytes, with various viscosities and temperatures.

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In order to study low-frequency cardiac vibrations less than 20 cps, the vibration at various points within the esophagus has been recorded by a strain-gauge transducer connected with a water filled No.13 cardiac catheter whose end was coveredby a small rubber balloon.
The curves of the vibrations recorded by this method were found to be greatly affected by the mode of tubing systems. Thus, for the purpose of an accurate analysis of the curves, the frequency and transient response characteristics of the tubings and the timing delay due to transmission of the pressure in the tubings were studied by application of the sine-wave and square-wave pressure vibrations under various conditions. Results were as follows : The resonant frequency of the transducer and amplifier without tubings was 95 cps and the response curve was flat up to 80 cps. The resonant frequency became lower and the damping effect or the transmission time of the pressure increased in proportion to the length as well as the narrowness of the catheter. These tendency were more remarkable in the case of a polyvinyl tube. When stopcocks or a lead tube were inserted between the catheter and transducer, the resonant frequency decreased but the transmission time a little increased. The range of resonant frequency of the present study was 6-27 cps, the damping ratio 0.06-0.33, and the transmission time 5-16 msec.
When a three-way stopcock and a lead tube of 40 cm length were inserted between the transducer and No. 13, 120 cm catheter, the resonant frequency was 12 cps, responses over 20 cps greatly attenuated and the ransmission time was 7 msec. Therefore, this tubing seemed to be desirable, practicable in the intraesophageal recording.

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For the study of intracellular potential recording, authors made an atempt to devise a two stage d. c. pre-amplifier with negative capacitance circuit using selected N-channel J-FET (Junction-Field Effect Transistor, Toshiba 2 SK 13) whose gate current was within a range of 10^-12A at 25°C. In the 1st stage amplifier, the differential circuit of the source-follower principle was adopted. In the 2 nd stage amplifier, the differential circuit of the drain-follower principle was employed with the J-FET. Negative capacitance was applied to the input through a 10 pF capacitor connected with the one stage a. c. amplifier having variable gain of 2-3 times.
The pre-amplifier was stable in operation and worked linearly in a range of ±1.0 V of input voltage (the gain was 5x). This satisfactorily amplified the applied square pulse of 1.0 msec duration as the original form in practical use. The noise voltage was about 0.3 mV under just compensation when the input resistance was 100mΩ. This device is a compact, light and shock-proof one and is suitable for electrophysiological recording from superfine microelectrodes. The power source is very easily simplified because of low consumption of electric power, thus this can take the place of tube pre-amplifier and is better than the MOS-FET pre-amplifier in several features especially in a very low noise.

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