抄録
By means of measuring the pressure changes in the middle ear cavity caused by the spontaneous contraction of the middle ear muscles of the anesthetized guinea pig, the genesis of the spontaneous contraction was studied. The results obtained in this work were summarized as follows:
1) The spontaneous contraction of the middle ear muscles was observed in almost all of the animals tested. The amplitude of the pressure changes in the middle ear cavity during spontaneous contraction was on the average 1.2mmH2O and its duration averaged 1 second.
2) As concerns the frequency of the spontaneous contractions, there had been never observed a regularity or periodicity and the frequency decreased with time. There were also found great individual differences.
3) By means of the simultaneous recording of electromyogram, it became clear that the spontaneous contraction had no relation with the activity of the striated muscles in the body.
4) The spontaneous contractions were inhibited during sound stimuli of high intensities, pain stimulus and contact stimulation. On the other hand, light anesthesia and asphyxia promoted the occurrence of the spontaneous contractions.
5) These results indicate that the spontaneous contractions are not related to the movements of the striated muscles in the body, but have great relation with the situation of autonomic nervous systems.
