725 
from the model in wax, refer to an animal that does not belong to 
this series, a striking resemblance can be stated between the changes 
of direction observed and those that could be anticipated with 
reference to the model. 
The fact, however, is that with none of the rotations I—III does 
the horizontal semicircular canal attain horizontality. Dr BurLer and 
Kosrer's researches showed that the right horizontal semicircular 
canal is approximately horizontal when the animal turns from the 
ventral position about 30° round the bi-temporal axis with the head 
down and at the same time round the fronto-occipital axis about 
7° to 8° with the left eye downwards. 
We examined different animals in this position, from which it 
appeared that in most cases the nystagmus had not disappeared alto- 
gether and could neither be made to disappear by applying different 
Variations in the rotation round the said axes. We observed, how- 
ever, that the nystagmus-movements are very small in this position. 
Only in two cases could the nystagmus be made to disappear 
completely, viz. with a rotation about the bi-temporal axis of 37° 
in the one and 30° in the other rabbit and combined with a rota- 
tion about the fronto-occipital axis of 5° in both animals. 
This urges us to conclude that the horizontal semicircular canal 
plays a principal part in caloric stimulation, that, however, in most 
cases also the vertical canals exert some, though a small, influence. 
This influence, however, was not such as to enable us to make an 
accurate analysis of it from the curves. 
For a positive solution of the problem it would be necessary to 
determine in one and the same rabbit the nystagmus in various 
positions of the head in space, as well as the compensatory eye- 
positions in the said positions and finally through microscopic exa- 
mination of the labyrinth, to determine accurately the position of 
the semi-circular canals in that animal, after the method of Dr 
3urLET and Koster. 
| Ji 
Wig. 8. 
