724 
determined for the various rotations, i.e. the point at which the 
horizontal semicircular canal has reached its optimal horizontality 
and consequently no or hardly any streams can exist in this canal 
after douching the meatus. This determination was performed with 
the aid of a model in wax!) formerly made of the semicircular 
canals of a rabbit, which contrivance was arranged, after the indi- 
cations of DE BurLer and Kostpr?), so as to afford an exact imitation 
of their natural position in the rabbit’s skull. 
This was to the following effect: 
With the animal in ventral position with horizontal mouth-fissure 
(Fig. 5) the level of the ampulla of the horizontal semicircular 
canal is higher than the canal itself, so that an ampullo-fugal endo- 
lymph-stream will occur on a cold-water douche of the meatus. 
With rotation I the horizontal canal is approximately horizontal 
at 40° (Fig. 6). 
With rotation II the horizontal canal is approximately horizontal 
at 150° (Fig. 7). 
With rotation III the horizontal canal is approximately horizontal 
at 57° (Fig. 8). 
In figures 2—4 these points are indicated with crosses. At a 
glance it may be seen that a marked change in the nystagmus occurs 
at the very place where the horizontal canal is approximately horizontal. 
When taking into account the considerable individual variations 
in the position of the semicircular canals in various animals of the 
same species, and when also considering the fact that our results 
are based upon the observation of tive different animals, while the 
correction for the compensatory eye positions as well as the data 
Fig. 7. 
') H. M. pe Burver and A. pe Kreun. Ueber den Stand der Otolithen- 
membranen beim Kaninchen. Pfliig. Arch. Bd. 163. (1916) S. 321. 
*) H. M. pe Burver and J. J. J. Kosrer. Zur Bestimmung des Standes der 
Bogengänge und der acustica im Kaninchenschädel. Arch. f. Anatomie und 
Physiologie. Anatomische Abteilung. (1916) 59. 
