TONIC AND PHASIC CONTRACTIONS OF THE RETRACTOR PHARYNGIS OF SNAIL (EUHADRA LUBUANA)

抄録

1. Excised retractor pharyngis of snail responds to various types of electric current with tonic and phasic contractions. The results confirm in part the findings of Winton and Singh, and also in agreement with Kawabata's opinion that all responses to electric stimuli contain both phasic and tonic componennts, the latter being most conspicuous in the response to intense single induction shocks.
2. Tonic contraction and relaxation at the polar regions were observed microscopically and the pattern of responses was classified into two types. The response in the first type is marked with vigorous reactivity at the cathodal region and generally found in summer experiments, while those in the second type with anodal responses and often encountered in winter. Responses in one type are capable of transition into those of the other type in the same preparation by changing the ionic milieu.
3. The strength-duration curves were plotted with regard to both closing and opening stimulations, and their relation to both types of polar effects were discussed.