Physiology. — “Tonic reflexes of the labyrinth on the eye-muscles’’. 
By Prof. R. Magnus and A. pr KreIJN. 
(Communicated in the meeting of June 28, 1919). 
It is a well-known fact, that the labyrinths strongly influence the 
position of the eyes in the orbits. Each position of the head namely, 
corresponds to a special, definite position of the eyes in the orbits. 
The inquiries concerning the relation between the position of the laby- 
rinth and that of the eye is highly impeded by spontaneous movements 
of the eyes and it is, therefore, easy to understand that more elabo- 
rate investigations were made almost exclusively with animals, which 
make but few such spontaneous movements. Among the animals, 
which are usually experimented on, the rabbit is preferred to all 
others. | 
In 1917 an extensive publication on this subject was issued 
by the pharmacological Institute *), in which the question of the 
relation between the positions of the labyrinth and of the eye was 
examined as completely as could be. Starting from a primary position 
of the head with a horizontal mouth-opening and the lower jaw 
pressed downward, other positions of the head appeared to involve 
both constant vertical deviations of the eye and rotatory movements; 
as for side-movements, in the direction of the eye-opening, no reliable 
data could be found. 
The vertical deviations of the eyes always take place in 
opposite directions for the two eyes, whereas the principal deviations 
were found with the head in the two side-positions, when the upper 
eye deviated as much as possible downwards, the lower eye in the 
same degree upwards. 
The rotatory movements always take place in the same direction 
for both eyes, the greatest deviations were found, when the head stood 
with its muzzle vertically upwards or downwards. During the expe- 
riments the rabbits were put immovably in various positions with regard 
to their surroundings, when special care was taken that any shifting | 
of the position of the head with regard to the trunk was out of 
1) J. v. pb. Hoeve und A. DE KLEIN. Tonische Labyrinthreflexe auf die Augen. 
Pfliigers Archiv. 169. 241. 1917. 
