Physiology. — “On the Effect of Tonic Labyrinthine and Cervical 
Reflexes upon the Eye-muscles’. By Dr. A. pe KrryN (Com- 
municated by Prof. R. Maanrts). 
(Communicated at the meeting of April 23, 1920). 
Recent researches performed in our Institute have shown that in 
various animals the tonus of the skeletal muscles varies, according 
to fixed laws with the position of the head, and that the reflexes 
which come into play here, may be divided into two groups: Tonic 
labyrinthine reflexes, which appear when the position of the head 
in space is changed, and tonic cervical reflexes which appear when 
the position of the head relative to the trunk is changed. Our object 
in this paper is to ascertain how far these reflexes can be demon- 
strated as well for the eye-muscles. 
[. Tonic labyrinth-refleves acting on the eye-muscles. 
Many times already tonic labyrinth-reflexes have been examined 
in man and in various animals; they are the so-called compensatory 
eye-positions. 
Some years ago an extensive quantitative investigation in rabbits 
was published in Pfliiger’s Archiv *). 
_ For further particulars we refer to this publication; we wish to 
lay stress once more on the following final results: 
a. With every position of the head in space we note a corre- 
sponding position of the eyes in the orbita. 
6. If the head is brought from one position into another, the eyes 
attain their new position in the orbita either by rotatory or by vertical 
-movements, or by both together; no data could be obtained for lateral 
movements in the direction of the palpebral aperture. 
_ Neither was Bensamins’*) more successful in his experiments with 
fishes. 
c. It is allowable to state generally that, if the head passes from 
1) J. v. p. Hoeve und A. pe Kreyn. Tonische Labyrinthreflexe auf die Augen. 
Pfliigers Archiv. fiir die ges. Physiologie. Bd. 169. S. 241. 1917. 
3) C. E. Bensamins. Contribution à la Connaissance des Réflexes toniques des 
muscles de l'oeil. Archives Néerlandaises. Tome II, 4e livraison, p. 536 (1918). 
j 33 
Proceedings Royal Acad. Amsterdam. Vol. XXIII. 
