Physiology. — “The function of the Otolithes’. By Prof. R. Maenus 
and A. DE KLEYN. 
(Communicated at the meeting of Sept. 25, 1920). 
In the course of the last half century an infinite amount of literature 
has appeared upon the functions of the vestibular organ. From the 
first, anatomical research rendered it probable that a sharp distinction 
had to be made between the sensory epithelium in the cristae 
of the semi-circular canals covered by the so-called cupula and 
which can move freely in the endolymph, and between the sensory 
epithelium of the maculae of sacculus and utriculus which, covered 
by the otolithes with their greater specific weight, appears specially 
suited to react upon the greater or lesser pressure of the said 
otolithes. 
But, whereas our knowledge of the function of the semi-circular 
canals is fairly extensive and, moreover, the anatomical data agree 
fairly well with the clinical and experimental data, this is by no 
means the case with respect to the knowledge and theories regarding 
the function of the otolithes. 
This is due to various causes. If, as has been supposed in particular 
by Macu and Breuer, the function of the otolithes is determined by 
the greater or lesser pressure upon the sensory epithelium beneath, 
we may expect that the otolithes will have some influence upon 
those reflexes which come into play by changes in the position of 
the head, and that their influence will continue as long as this 
position remains unchanged and the pressure of the otolithes is constant. 
Or, in other words, that the otolithic reflexes are more particularly 
tonic reflexes. Up till a few years ago, tonic reflexes of the labyrinth 
were known only in the form of compensatory positions of the 
eyeball, and therefore the function of the otolithes had to be studied 
exclusively from these reflexes. As, however, our knowledge of these 
positions was still far from complete, and sufficient investigations 
had not been made, it is obvious that the literature on this subject 
will contain opinions of a more or less speculative nature. Moreover, 
the influence of the clinique was inhibitory. While, clinically, the 
different vestibular reactions upon (rotatory) movements were in- 
vestigated more and more carefully and began to assume an ever- 
increasing importance in the diagnostics of the diseases of the labyrinth, 
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