Abstract
Employing single myelinated nerve fibres which were dissected out of sciatic nerves of the toad, observations were made on various actions of weak narcotic and NaCl-deficiency upon the nodal activity. Results obtained are as follows:
1. The urethane concentration just critical for conduction block is certainly smaller than that for excitation block.
2. There is a small range of stimulus near the threshold, where the spike of a normal node appears graded. The range gets wider with larger narcotic concentration, and, at the same time, the spike height gets smaller until it vanishes finally, leaving the local response behind.
3. In advance to the range of graded spike mentioned above, there is another range of stimulus where the local response appears. The local response gets larger almost linearly with stronger stimuli, up to a certain maximal value, which gets larger in stronger narcotization.
4. Narcotic and NaCl-deficiency are co-operative in bringing forth conduction block.
