950 
The normal animal was first examined, on “Labyrinth-Stellreflexe’’, while held 
up in the air, that is, before the bilateral labyrinthextirpation performed on it. 
In this experiment the eyes were blindfolded beforehand. The result was to the 
following effect: 
Animal, held up free in the air by the pelvis. 
Normal position of the pelvis: Head in normal position. 
Held up on its right and left side: Head about normal (deviation + 30’ from 
the normal position). 
With its back placed in horizontal position: Head brought in normal position, either 
because the front of the body i.e. the neck and the upper part of the thorax is 
bent ventratward, or because the front of the body performs a spiral rotation 
of 180°. 
Animal suspended with head downward: Head and muzzle are held vertically 
downward; the neck, however, is distinctly dorsi-flexed. 
Animal suspended with head upwards: Head in normal position. 
When carrying out the experiment without the eye-bandage, the result is 
precisely the same; only the head is brought into a perfectly normal position 
when the animal is held up free in the air, horizontally placed on its side. 
On the 6th of June 1919 a bilateral extirpation of the labyrinth was performed. 
Some hours after the operation the animal keeps its head straight and no 
nystagmus is seen. Neither in this investigation nor in any of the following did 
the animal prove to possess any labyrinth-reflex. 
June 7. 1919. When investigating in the air without the eye-bandage (so with 
open eyes) it appears that the animal does not possess any “Stellreflex” in 
the ar. 
Holding the animal in horizontal direction on its right or left side: Head falling 
to the right, resp. to the left side. 
Holding the animal in horizontal direction on its back: Head falls on its back. 
Suspended with head downwards: Head held as lying on its back. 
Suspended with head upwards: Head in various positions (now latero-flexed to 
the right or retro-flexed). 
From this investigation we conclude that on the day after that 
of the operation (bilateral extirpation of the labyrinth) the animal, 
when held up in the air, does not dispose of ‘Stellreflexe”’ and the 
eyes do not act compensatively. 
An investigation of other dogs gave evidence that after bilateral 
extirpation of the labyrinth the animals gradually recover the ability 
of bringing their heads into the normal position again when they 
are held up in the air. It was also evident that the animals obtain 
this ability through the eyes and by fixing different objects around 
them. When the eyes are blindfolded, the “Stellreflexe” will immediately 
disappear, so we have to do with optic “Stellrefleve”. 
We have not made an inquiry of the successive appearance of 
the optic “Stellreflexe” in the above-named dog, since it was one . 
of the first dogs, in which “Stellreflexe’” were found and these had 
already been fully developed at that time. 
