1) It is demonstrated that there exist efferent sympathetic pupilloconstricting fibers in the cervical sympathetic trunk of cats and rabbits besides so far accepted efferent sympathetic pupillodilator fibers.
2) The efferent pupilloconstricting fibers in the cervical sympathetic trunk have no cell stations in the superior cervical ganglia.
3) The results of 1) and 2) are correspondent with already verified results referring to the pupilloconstricting action of “efferent posterior sympathetic nerves” of cold blooded animals. In analogous to cold blooded animals, the present experimental results lead to conclude that “the efferent sympathetic nerves” of warm blooded animals such as cats and rabbits are possessed with pupilloconstricting actions.
4) It is assumed that the dilator muscle of the iris of cats and rabbits are subject to “efferent double sympathetic innervation”.
