The experiments1 reported here were carried out in an attempt to localize the labyrinthine tonic influence to some particular part of the labyrinth. A more detailed report of some of the experiments will appear in Pflüger's Archiv für die gesamte Psychologie, 1926; here I wish especially to report some interesting points with practical bearing which arose in the course of this work.
It has been shown by Magnus2 and de Kleijn 3 that the well-known diminution of tonus following unilateral labyrinthectomy is composed of two factors: the one permanent, which is a tonic-neck reflex evoked by the turning of the head; the other a passing influence of labyrinthine origin, which is still present after the turning of the head is corrected. They also showed that the latter diminution of tonus does not occur following the injection of cocaine in one labyrinth in the guinea-pig. Arndts 4 has