In 1951 and 1952 I researched some physical characters of two populations (X and Y group) which married whithin limited groups in Osaka.
The special features of these groups are as follows.
1) On the A. B. O blood groups, X group has more O type than gernral Japanese and Y group has many B type for the Japanese. (Table 1 and 4)
2) On the finger prints, there is a tendency that both groups have many whorl type and few ulnar loop type.(Table 2 and 5)
3) On the some measures, both groups have lower cephalic indices.(Table 3, 6, 7 and Fig. 1-7)

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Five students of Japan Women's College of Physical Education were used as the subjects. They were asked to put on an apparatus like the one shown in Fig. l for fixing the elbow or ankle joint at various angles. While either one of the main limb muscles(M. biceps brachii, M. triceps brachii, M. tibialis anterior, or M. gastrocnemius) was kept in a sustained isotonic-isometric contraction, electromyogram of the test muscle was led by the bipolar surface electrodes. For the frequency analysis an automatic frequency analyzing integrator was used. It has seven separate filtering frequency bands whose frequency characteristics are shown in Fig. 2.
The results are summarized as follows
1) The frequency spectra of the electromyogram were obviously influenced by electrode conditions as the interelectrode distance (Figs. 5 & 6), their relative position to the muscle belly (Fig. 8), and their angles to the direction of muscle fibers (Fig. 9). These different electrode conditions brought about in some cases the increase in the ratios of higher frequency components or in others the increase in the ratios of lower frequency components. No systematic tendency was observed in the ratios of each frequency components corresponding to the changes in electrode conditions.
2) As shown in figures in the present paper, 47-50 cps components known as Piper rhythm was not always dominant. In some cases, considerably higher frequency components, 300 cps or higher, were the dominant ones in frequency spectra.
3) The influence on the ratios of each frequency components of the change in the level of contraction was almost negligible (Figs. 16 & 17).
4) Changes in the length of the test muscle caused by the changes in the angle of the elbow or ankle joint affected heavily on the frequency spectra. It was disclosed that, irrespective of the muscle tested or the difference in electrode conditions, the increase in the lower frequency components was more marked when the muscle was stretched more intensely (Figs. 10-15).
5) Because of the wide range in the fluctuation of frequency spectra (Figs. 4, 18 & 19), it was very difficult to determine the dominant components and to find the difference of frequency components in different test muscles.
Since the day of Piper, it has long been known that frequency components of the electromyogram bear a special relation to the grouping of activities of different motor units. On the other hand, the recent study on gamma motor system has disclosed some asynchronizing effects of muscle spindle impulses upon the activities of alpha motoneurones. Besides, the asynchronizing effect is considered to be connected with the occurrence of the higher frequency components of the electromyogram.
The results of the present investigation, however, can not been explained on the basis of clear-cut association between the asynchronizing effect and the higher frequency components. The result that the increase in the lower frequency components was much more marked when the muscle was more strongly stretched is contrary to the expectation from the asychronizing effect. Therefore, the antagonizing mechanism to the asynchronizing effect has to be suspected to explain the above results. From the viewpoint of autogenetic regulation, it may be assumed that the antagonizing mechanism lies proprioceptively in the tendon afferents.

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[in Japanese]

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