Abstract
The periodic contraction in the isolated lung of the Japanese toad was observed and the necessary condition for its occurrence was analyzed.
The periodic contraction is apt to occur in summer rather than in winter, and its rhythm is about 10-20/hour in summer and about 4-12/hour in winter.
The temperature coefficient of the rhythm is 2.3 in average and shows no seasonal variation, The rhythm and size of the periodic contraction are hardly influenced by such drugs, as autonomomimetic, autonomic blocking, anesthetic agents etc., but markedly by the change of the ionic environment or the muscle stretch.
The periodic activity is myogenic in origin, and its development may closely be related to the ionic condition.
The periodic contraction may be regarded as a rather non-physiological contraction provoked by changes in environmental conditions, which result inevitably from the isolation of the lung and other experimental procedures.
