Physiology. — “On the question whether or no Darkness-nystagmus 
in dogs originates in the Labyrinth’. By A. pr Kieyn M.D. and 
C. R. J. Versreren M.D. (Communicated by Prof. R. Maenus). 
(Communicated in the meeting of September 27 1919). 
An extensive clinical examination of miners induced Oum to believe 
that the nystagmus, common among this class of people, originates 
in the labyrinth. 
Raupnitz’s discovery that nystagmus is elicited in dogs after a 
prolonged sojourn in the dark has enabled Onm to adduce experi- 
mental evidence for the above hypothesis. 
He starts from: the consideration ‘dass der bei jungen Hunden 
durch Dunkelheit hervorgerufene Nystagmus in Bezug auf Ablauf, 
Ausschlag und Dauer der Zuckung, den Einflusz der Ruhe und 
Bewegung mit dem Augenzittern der Bergleute volkommen über- 
einstimmt”. 
He then proceeds by describing some experiments in which he 
has tried to perform bilateral labyrinth-extirpation in dogs suffering 
from darkness-nystagmus. 
In this effort he failed, except once, when the laboratory animal 
did not show any more symptoms of nystagmus. However, it was 
so weak that it died some days afterwards. 
From this doubtful success Onm concludes that the labyrinthal 
origin of darkness-nystagmus has been established. 
By a more effectual method of labyrinth-extirpation we were so 
fortunate as to demonstrate that: 
Darkness-nystagmus in young dogs (Raupnitz, Onm) is not of 
labyrinthal origin. 
We found that: 
1. the existing darkness-nystagmus persisted after bilateral labyrinth- 
extirpation. 
2. darkness-nystagmus can be elicited even after bilateral labyrinth- 
extirpation. 
Fig. 1 shows the curve of this nystagmus. We see that the typical 
darkness-nystagmus is interrupted by a few spontaneous greater 
movements. The registration was performed by attaching a wire 
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