Abstract
1. In the adult female, the electrical discharge of M. bulbocavernosus and M. transversus perinei superficialis showed a weak cyclic change with the menstruation cycle, decreasing or vanishing around the bleeding period and, restoring thereafter. With M. sphincter ani externus and M. triceps brachii, no such remarkable reduction was observed.
In male, such a cyclic change could not be detected.
2. The inhibitory action of progesterone, and human chorionic gonadotro. phin, and the enhancing action of estrogen and androgen were demonstrated on the tonus of M. transversus perinei superficialis and M. triceps brachii in the female subjects. The male subjects responsed with much lesser degree. With M. sphincter ani externus, effects were less marked than those on the other perineal muscles.
3. After the intravenous administration of 1 unit oxytocin, the perineal muscle group of female subjects showed diminished discharges or their disappearance regardless of the sexual cycle. On the other hand, those of male subjects showed slightly increased discharge with exception of the external spincter ani muscle which was hardly changed by oxytocin.
The brachial triceps muscle, both in female and male, on the other hand, showed increased discharge.
4. With progesterone and oxytocin, it was demonstrated that effects of the hormone on the muscular tone are different among various sorts of skeletal muscle. From this fact together with the authors' previous reports, it was presumed that the changes in electromyogram due to hormones may be the result of their combined effect upon the nervous system and the muscle itself. It was also emphasized that, effects of progesterone and oxytocin upon tonus of abdominal and perineal muscles are useful to promote gestation and parturition respectively.
