394 
tbrough the anaesthetized cornea and by thus transmitting the move- 
ments to a lever. 
3. the darkness-nystagmus behaves towards a super-added vestibulary 
nystagmus in a different way from a vestibulary nystagmus, i.e. if 
we impart a vestibulary stimulus to a dog suffering from darkness- 
nystagmus, thus evolving an additional vestibulary nystagmus, the 
two forms of nyst. will be seen to persist concurrently, without 
exerting any influence upon each other. 
If, however, we superadd to an existing vestibulary nyst. (e.g. 
caloric) a second vestibulary nyst. (e.g. rotatory nyst.) the first nyst.- 
deflections will be seen to be slightly irregular and of different 
magnitude, but the effect would seem to be rather a resultant of 
two movements. 
Fig 1. Fig 2. 
Fig. 2 illustrates the typical instance of what is called the com- 
bination of darkness-nystagmus and caloric nyst. The minor deflections 
represent the movements of the quietly proceeding darkness-nystagmus ; 
the larger waves show the eye-movements provoked by irrigating 
the ear with cold water. 
We cannot say here in how far Oum is justified in looking for 
the origin of the miners’ nystagmus in the labyrinth, but we feel 
confident in asserting that he is wrong in assigning the cause of 
the darkness-nystagmus in dogs to the labyrinth. 
(Pharmacological Institute of the 
Utrecht- University). 
