261 



7/6 1921 : Animal sits symmetrically, no eye-deviation. 



Reactions of semicircular canal : all positive. 



Tonic reflexes : all lacking. Asymmetrical phenomena quite gone as 



in cocain-test. 

 8/6 1921 : Like previous day. When sitting, head sometimes turned very slightly 



to the right, for the rest animal sits symmetrycally, no eye-deviations. 



Anatomical examination by Dr. M. de Bürlet. All otolithic membranes detached. 



Right sacculus ; sensory epithelium without membrane ; the otolithic membrane 



isolated in the sacculus between ductus endolymphaticus and the 



back-part of the sensory epithelium. 

 Right ulriculus; sensory epithelium without membrane; the otolithic membrane lies 



between the posterior portion of the macula and the entrance to 



the crus commune. 

 Left sacculus; sensory epithelium without membrane: the otolithic membrane 



rests against the lateral wall of the sacculus and above the macula. 

 Left utriculus : sensory epithelium without membrane; the otolithic membrane 



is detached towards the inner side and above the macula but lies 



in the utriculus. 



These experiments go to show that for more than a week after 

 the removal of the otolithic metnbranes the sensory epithelium is still 

 in a constant condition of stimulation. When one labyrinth is for 

 some time eliminated by cocain, the stimuli emanatmg from the 

 non-injected labyrinth will induce asymmetrical phenorïiena, similar 

 to (hose after unilateral extirpation of the labyrinth in normal 

 animals, with this difference, however, that in the centrifuged 

 animals injected unilaterally with cocain, these phenomena do not 

 change with a change of position of the head in the air. 



Considering that there was a week's wait after the centrifugalion, 

 it is probable that the above condition of stimulation should no 

 longer be ascribed to centrifugation, and that, therefore, to the 

 sensory epithelium of the maculae the power should be assigned of 

 eliciting stimuli, which, owing to the absence of the otolithic mem- 

 brane, do not vary much as to strength. 



The function of the otolithic membranes, then, consists in altering 

 the intensity of this condition of stimulation of the sensory epithelium. 

 This stimulation will be stronger or weaker according as the mem- 

 branes pull at the epithelium or press upon it. 



Relative to the portion of the sacculus (the main pp,rl) innervated 

 by the N. saccularis it has been previously demonstrated that the 

 stimulation decreases with pressure and increases with pulling. This 

 mechanism exists probably also for the utriculusmaculae. 



17 



Proceedings Royal Acad. Amsterdam. Vol. XXV. 



