Abstract
1. Toad's bladder responds to various types of electric current with phasic and tonic contractions. The response to indirect stimulation delivered to the vesical nerve consists almost exclusively of phasic contractions. Responses due to direct stimulation consist of both phasic and tonic components contained in different proportions depending on the current form. Response to A. C. stimulation consists, alike indirect stimulation, mainly of phasic components, while those to intense single induction shock and intense D. C. are almost exclusively tonic.When an A. C. is made into an unidirectional pulse current by passing through a vacuum tube, the response becomes strikingly tonic.
2. Phasic contractions can be propagated in nature, and are actually propagated to a certain degree according to the nature of the tissue. Conditions necessary for evoking phasic contractions are considered qualitatively similar to those of nervous impulses or twitches in skeletal muscle.
3. Tonic contraction is nothing more but a temporary change in grade of contracture or tone. It can not be conducted and does not show the all-or-none relation. Its occurrence has some relation to the duration of unidirectional current flow, as well as to current intensity.
4. Weiss' formula applies considerably well with strength-duration curve measured by taking phasic contractions as indicators. Rheobases were 3-5μA, chronaxie 0.35-0.4 sec. at 20°-25°C
