AN INVESTIGATION OF INHIBITION BY DIRECT STIMULATION OF THE TURTLE'S HEART

Abstract

Effective intensity-frequency relationships causing inhibition by direct repetitive stimulation of the turtle heart were investigated. Prevention of the inhibition by atropine, its prolongation and reinforcement by eserine and its similarity to effects of vagus stimulation and to acetylcholine soln. are considered as probable evidence that inhibition by direct repetitive stimulation is due to liberation of acetylcholine at vagus terminals. The turtle''s ventricle which is not inhibited by acetylcholine and receives no vagus fibers does not show this type of inhibition.