The heart in ascidians consists of a tube open at both ends, and which, by its contraction, drives the visceral fluid alternately towards the viscera and away from them. Its action does not seem to depend on the nervous ganglion lying between the oral and anal sac, or indeed upon nervous influence at all.

The application of an induced current causes it to beat for some time in one direction instead of alternately, but does not arrest its pulsations.2 According to Krukenberg it is not affected either by atropine or muscarine. It is paralysed by veratrine, quinine, and strychnine: these poisons rendering the beats gradually weaker and more irregular. No evidences of tetanus are to be seen from the action of strychnine. The mode of action of the heart is affected by helleborin and nicotine: helleborin increases the number of the advisceral beats while nicotine diminishes them. Camphor and strychnine have possibly an action in this respect resembling helleborin.