SECTION XXII 

 THE SENSE OF EQUILIBRIUM 



CHAPTER LXV 

 THE SENSE OF POSITION* STATIC SENSE 



The Otolithic Cavity. — This organ is usually represented by a 

 membranous saccule which is placed in the integument in free com- 

 munication with the outside. Its epithelial Hning is beset with 

 long hair-Uke processes, the tips of which are weighted with small 

 concretions of calcium carbonate, known as otohths. Many of 

 these granules rest free among the hairs. The general structure of 

 these otocysts has led physiologists to believe 

 that they are quite unable to oscillate in unison 

 with the vibrations in the surrounding medium 

 and cannot, therefore, play a part in the recep- 

 tion of sounds. For this reason, it is now com- 

 monly held that they are concerned with equili- 

 bration and more particularly with the percep- 

 tion of position than with that of motion; i.e., 

 with the ''static" rather than with the "dyna- 

 mic" sense. 



This conclusion has a definite experimental 

 basis, because if the otolithic material is re- 

 moved, the animal shows disturbances in its 395— t o 

 position and movements. Thus, the destruc- u-mic Cavity Showing the 

 tion of the otocyst in crustaceans gives rise Lining Cells with their 

 to a tilting of the head toward the side on which h^^^-™ Pbolongations 



1 ... 1 ^» r>. ' 'Ml ^^^ "^^^ Otoliths. 



this injury has been effected. Quite similarly, 



if made to move, this animal invariably moves about in a circle, return- 

 ing finally to the place from which it started. The same result may 

 be obtained by cutting the nerves innervating these organs. It 

 seems, therefore, that the otocyst and otolith should really be named 

 statocyst and statolith respectively.^ This nomenclature seems to be 

 indicated the more, because Kreidl,^ has succeeded in varying the 

 equilibration of the crustacean palemon by changing the contents of 

 its statocyst. At the time of molting this animal fills its statocystic 

 cavities with granules of sand to tide it over this particular period. If 



1 Von Buddenbrock, Sitzungsber., Akad., Heidelberg, 1911. 



2 Sitzungsb., Akad. zu Wien, cii, 1893, 149. 



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