Hitherto, not only the instruments and apparatuses supplied from engineering field, but theories for engineering also must be brought into the medical field. Among all, theories for signal detecting problem is perhaps some of the most useful tools to be applied for medical purpose.
These theories have been developed mainly in the communication engineering field and have made great strides recently by the aid of the information theory.
The methods of time series analysis, for example, the correlation function method and the periodgram method are useful for detecting any periodic components hidden by noises. The matched filter can be used when the shape of signal pulse is known.
Sometimes, the average response computer searches very delicate reactions induced any periodic stimulus.
The concept of pattern recognition has important connection with the signal detection, because any signals, generally speaking, are recognized as patterns.
Quick detection makes use of the process of the adaptive control. A direction finder capable of learning is shown as an example.
The rational criterions for judging whether signal is present or not are given by the decision theories, for example, by the stochastic decision theory.
Signals must be displayed from the human engineering point of view. An example of display hereof is presented.
Finally, the importance of the operations research is emphasized for any proiect of signal detection.

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According to the experimental works in our institute, the mechanisms of ultrasonic therapy was explained practically. These experimental items are as follows ;
1.On the characteristic heat produce during the application of ultrasonic waves in the living tissues.
2. The sciatic-tibialnerve preparation excised from Bufo vulgaris was used for the purpose to resolve an effect of ultrasonic waves on nerve excitability and paralysis, especially on the difference between the ultrasonic paralysis and the paralysis by heating.
3. Effect of ultrasonic waves on absorption of Dye (Phenolsulfophthalein) from the skin and muscles and renal function.
4. An increase in permeability of capillary arteries of human forearm after the application of ultrasonic waves.
5. Effect of ultrasonic waves on the function various organs (liver, gall bladder, kidney, heart and stomach).
6. In dication and contraindication in the ultrasonic therapy.
7. Analgetic effect by the ultrasonic waves to Neuralgia and the similar diseases.
Insummary, the ultrasonic therapy was thought to be useful with other physical therapy various diseases.

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The apparatus, the method and the clinical application of the echo-encephalography are being reviweed. This ultrasonic investigation is found to be very useful in detecting the intracranial space-occupying lesions by observing the deviation of the third ventricle. However, since the diagnosis is achieved only by indirect means, this method could not be said to be as satisfactory as that of cerebral angiography. Nevertheless, the investigation is totally painless and harmless to the patient and easy to handle, it is very useful for emergency purposes.
The element of the transceiver is made of Barium titanate, and its frequency is 2 Mc/sec. 15 mm in diameter with flatt surface. The acoustic power of the transmitter was estimated about 1. 5 mW/sq. cm in mean intensity on one probe.
We succeeded to improve the apparatus as follows ; 1) by transistorizing the main part of the apparatus completely, the size became smaller, and the weight lighter. 2) to detect if the two ultrasonic beams, which are projected through the temporal regions on both sides, ar on a line, the apparatus is designed to characterize by annexation of transmission and reflection method.
Beside from observing the lateral shift of the midline echo, we observed many cases of doubling of it which is thought to be due to dilatation of the third ventricle ; for instance, internal hydrocephalus, postepileptic and posttraumatic cerebral atrophy.
In addition, destructive effects to the nervous tissue, as a result of using lower intensity ultrasound, is studied experimentally and it is found that irradiation for a long duration (over 6 hours) creates some lesions of the nervous tissue, by raising the G. O. T. level of the cerebrospinal fluid, although it is totally harmless in cases of clinical application where the time of irradiation is only for a few minutes.

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Two types of decision rule for metrical diagnosis are presented in this paper. One of these is a method of simplified linear decision functions, which permits reliable results when suitable variables corresponding to the symptoms are chosen. The other type of decision rule is a method of self-organization of decision functions, which is a procedure to obtain reliable decision functions.
As an application of these methods, experiments of metrical diagnosis for congenital heart diseases are conducted. Further, as the hardware of decision procedure, an optical computer for linear decision functions and an electric computer for logical decision functions are proposed. In the conclusion of the paper, the problems of errors in decision processes are discussed.

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It was discussed that the so-called biological potentials are always recorded by elucidating some magnitude of current which biological tissue generates. Larger necessary current for the record needs better non-polarizable electrode and lower resistance.
If the biological potential is of short duration, e. g. nerve fiber action potential, use of non-polarizable electrode is not always necessary. In this case, however, better record can be expected if the polarization effect is minimized by smaller current passing through the electrode. This condition is attained by the high input resistance amplifier.
It was also discussed that smaller size of the recording electrode can result in larger potential and that easier access to the tissue can be attained by the development of some convenient types of polarizable recording electrodes.
It was mentioned that electrodes of high resistance frequently have troubles of noises and other interferences which are difficult to decrease. It is also possible that slightest movement of the leading wire can be the source of artefacts in the records. These and other unidentified deflection often could be minimized by the use of low noise wire with graphite sheath.

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