Abstract

Some of the first investigators to describe responses which can now be attributed to excitation of intramural cardiac nerve terminations were Bowditch (1871) and Ranvier (1880), both of whom worked on frog heart muscle, and Foster (1872) and Foster & Dew-Smith (1875) who worked on the snail heart. Gaskell (1883) observed that when Faradic shocks were applied to the atrium of the tortoise in a strength insufficient to stimulate cardiac muscle directly, a diminution and slowing of the beat was produced which, like the response to vagal stimulation, was mimicked by muscarine and prevented by atropine. Gaskell considered but rejected the possibility that Faradic stimulation excited vagal nerve fibres. The possibility that electrical stimuli applied to cardiac tissue can excite nerve fibres within it, has been re-appreciated only recently (see Blinks & Koch-Weser, 1963). This paper describes responses produced by field stimulation applied to a strip cut from the wall of the right ventricle of the chick heart. The results are compared with those obtained with similar preparations from the pigeon, rat, and guinea-pig. The work described in this paper formed part of a thesis approved for the degree of Doctor of Philosophy in the University of London. Brief preliminary reports of some of the results have already been published (Bolton & Raper, 1966).