抄録
It was shown that frog's ventricle respond with multiple firing accompanied by a long continued contraction in response to a single direct electrical stimulus when the concentration of Ca++ in the bathing Ringer's solution is raised up to about 8 times the normal concentration. This was shown to be due to the effect of excess Ca++ to localize the response by partial blocking, while a possibility of spreading the excitation to the whole ventricle still remains. The localization of the response was prevented by excess K+, epinephrine and by low temperatures. The spread of excitation was completely blocked by procaine or tetrodotoxin. All these conditions were found to inhibit the multiple firing accompanying a long sustained contraction, which is estimated due to an increase of Ca content in the ventricular tissue (a net gain). The net gain in the ventricular Ca content was found to be due to the result of multiple firing of the ventricle.
