The investigators of vestibular function are accustomed to use experimental animals in order to get an insight into the problem they have to deal with. When optokinetic nystagmus came into the realm of labyrinthology the difficulty was that this nystagmus could not be found in animals. Broers and de Kleyn examined a number of animals, but even in monkeys they did not succeed in finding it. At last some dogs proved to react to rabbits brought in front of them, on a rotating platform. They show a clear nystagmus of the head. The influence of various extirpations of parts of the central nervous system on this kind of nystagmus was investigated and the authors concluded that this nystagmus was optokinetical and stated that destruction of one cerebral hemisphere causes it to disappear and that section of one entire optic tractus leaves the optokinetical nystagmus unchanged.