Integrated circuits, though in appearance, being small electronic parts, feature as electronic circuits consisting of scores and hundreds of transistors, diodes, resistors and/or capacitors, and come under the category of micro-structures.
Integrated circuits are classified into three main types : semiconductor integrated circuits, thin film integrated circuits, and thick film integrated circuits. In addition, there is one type called hybrid integrated circuits, which is made by combining the manufacturing process of semiconductor integrated circuits and thin film or thick film integrated circuits.
when integrated circuits are compared with usual electronic circuits consisting of printed circuit board and some discrete electronic parts, integrated circuits, particularly semiconductor integrated circuits have distinguished features in reliability, in economy of costs, and as being micro-structures, etc.
As some features and conditions that medical electronic apparatus are required coincide exactly with those of integrated circuits, the use of integrated circuits in medical electronic apparatus is substantially the best policy.
However, at present time, the production quantity of medical electronic apparatus are so few that the development of particular integrated circuits for medical use only may not be economical. For that reason, I would advise application of general purpose integrated circuits to medical electronic apparatus.
At the present time, the use of integrated circuits can be recommended for the following medical electronic apparatus :
(1) Biomedical measuring equipments :
in D.C. amplifiers in electroencephalograph and electrocardiograph, etc.
(2) Telemetering equipments for medical use :
in transmitter parts to be placed directly on human body.
(3) Functional aids for human organs :
in hearing aids and buried type cardiac pacemaker.
(4) Medical data processing systems :
in digital circuits in general.

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The system of vascular branchings was considered to be very efficiently constructed for its physiological function and its structure and organization was analysed by the mathematical method of conditional extremum.
A vascular system with many branchings, for example the whole arterial tree, was regarded from its role as a duct system supplying necessary blood flow to the terminals, distributed in the body with constant pressure difference from the origin (from aortic pressure to precapillary pressure). The optimal structure of this system was reasoned as that of the minimum intravascular volume because as this volume decreases, the exchange rate of blood with substances in capillaries increases and the metabolic energy to maintain active blood decreases.
From these conditions, some formulae at the extreme were deduced and numerical solutions of optimal branchings were obtained for some typical examples of distribution at terminal points.
The minimum required volume of the whole arterial tree was estimated from standard values of the aorta (pressure, flow and diameter) and a very close value to the actual arterial blood volume was obtained.
A computed optimal structure to the peritoneal vascular branching showed close similarity to the original branching.

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The effects of left atrial pressure and myocardial contractility on stroke volume (S. V.) were analysed measuring the end-diastolic volume (E. D. V.) and the end-systolic volume (E. S. V.) of the left ventricle of the canine heart by the thermal dilution technics under constant heart rates.
The results of experiments showed that the left atrial pressure dominantly affected E. D. V., and that myocardial contractility affected E. S. V. On the change of cramped pressure of the left atrium about 30-40 mm H₂O, dE. D. V./dS. V. was more than 5 times of dE. S. V./dS. V., while on the change of sympathetic nerve stimulation from the left stellate ganglion (from 1 Hz to 6 Hz, 6 V) dE. S. V./dS. V. was more than 4 times of dE. D. V./dS. V.

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A method of making standardized chest roentgenograms is described.
This method can control X-ray exposure at each breath and circulation phases of the lung.
For detection of peak respiration, crystal thermister of the nose-mounted type is used. During the respiration, slight but rapid resistance change is registered by the thermister as respiration changes from inspiration to expiration, or vice versa, and amplified signal triggers switching circuit at the same time.
Instead of the ECG, photo-electric plethysmograph, which is made by CDS, and is mounted on a finger tip or an ear, is used for circulation pick-up.
When systole comes to an end, arterial pressure comes to peak value and the blood pulse wave rises rapidly, too; then, CDS's resistance increases, and the slight pulse signal through the amplifier triggers the circulation switch. This roughly corresponds to the T-wave of ECG.
Selection of each circulation phase is taken by a variable timer which can be delayed from zero to one second.
The two switched signals come to a coincidence circuit, and only when they coincide is the X-ray exposed.
By basic experiments, the ECG and blood pulse wave of 18 cases are compared with the time interval between the T-wave and the time when the pulse wave reaches 80% of its peak.
In the case of finger type, the time interval was 59.7±17.4 ms.
In the case of the ear type, the time interval was 22.7±6.5 ms.
The results of the basic experiments show that the ear type has less time interval than the finger type to the T-wave.
The standardization of chest roentgenograms is made easier by this method.
This method can be applied to a broad range of roentgenological studies.

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In measuring bioelectric signals from human body, biomedical electrodes play an important role as a connector between human body and electrical systems. In the human body-electrode systems, there are many troublesome problems; for example, drift or noise voltages originated from electrode surfaces and polarization impedance of the metal electrodes. These phenomena are the most fundamental ones which are common to all metal-electrolyte interfaces.
In this paper, the following DC properties of metal electrodes are experimentally investigated :
1) Floating potentials (half-cell potential) of metal electrodes such as Pt, Ag, Cu, W, Stainless steel and Ag/AgCl in physiological saline.
2) Relations of the floating potentials vs. temperature, pH and concentration and voltage fluctuations caused by flow of solution.
3) DC polarization resistances of metal electrodes in low current density.
4) Double layer capacitance which is in parallel with polarization resistance.
From the experimental results, it is found that offset voltage of a pair of Ag/AgCl electrodes is extremely small (below 0.1 mV) and stable compared with other inert metal electrodes. The Ag/AgCl electrode is the best in measuring DC or ultra-low frequency bioelectric signals.

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