THE EAR. 523 



THE FUNCTION OF THE INDIVIDUAL PARTS OF THE 

 MEMBRANOUS EAR. 



1. Utriculus, Saculus, and Semicircular Canals. 

 Regular auditory functions were formerly attributed to 

 these. The suggestion was even made that these struc- 

 tures aided in the perception of noises, while to the cochlea 

 was referred the perception of musical sounds. Such a 

 distinction is, of course, absurd at once, the difference 

 between noise and music being a physical and not a physi- 

 ological one. Later Florens and Goltz pointed out that 

 these structures were really not concerned at all with the 

 direct sense of hearing, but that they figured as organs of 

 equilibrium. Animals from which the semicircular canals 

 have been removed show the greatest difficulty in standing 

 still or moving readily and with precision. They seem to 

 be unable to tell the position of their bodies and show all 

 the symptoms ordinarily associated with intense dizziness. 

 An animal so robbed of these structures performs the most 

 senseless and awkward movements. It seems perfectly help- 

 less and is scarcely able to eat unaided. The question then 

 arises, in what manner these structures figure as equilibrium 

 organs. 



First. The three semicircular canals are arranged like 

 the three diameters of a cube, and so there is no motion 

 possible which does not fall in the plane of one or more of 

 these canals. 



Second. These canals are filled with endolymph which 

 is in communication at both ends with the utriculus and so 

 is able to circulate somewhat through these canals. 



Third. A movement of the head in any direction will 

 cause a backward flow of the endolymph in the semicircular 

 canal affected, due to the inertia of that liquid, just as in 

 the starting of a train the passengers by their inertia are 

 thrown backwards. This backward motion of the endo- 

 lymph affects the hairs projecting into it in the ampulla 

 somewhat like a stream of air over a field of grain, and in 



