194 THE HUMAN BODY. 



been differently stated by different physiologists. According 

 to Duges, the vestibule concentrates the sound, measures the 

 intensity, and consequently judges of the distance. It has 

 been supposed that the semicircular canals either give the 

 idea of the direction of the sonorous waves, and of the posi- 

 tion of the body from whence they emanate, or are simply 

 organs for increasing the sound. De Blainville thinks that 

 the function of the cochlea is to appreciate very acute sounds, 

 Duges makes it the musical portion of the auditory organ, 

 the appreciator of notes, and the special apparatus for the 

 perception of voices and articulate sounds. 



Other authors have thought that the spiral plate (lamina 

 spiralis), which narrows regularly from the base to the summit 

 of the cochlea, corresponds to the scale of notes, from the 

 gravest to the most acute, and that it vibrates in unison 

 with each one of them. 



According to Miiller and Longet, the object of the cochlea 

 is to furnish a solid plate upon which to spread the nervous 

 filaments, in contact with the bony walls of the labyrinth and 

 of the head, as well as with the fluid of the labyrinth; thus 

 being able to transmit to these filaments the vibrations com- 

 municated to the solid or fluid portions of the auditory 

 apparatus. And also, the spiral form of the cochlea gives in 

 the least possible space a relatively large extent of surface 

 for the expansion of the nervous filaments. 



This diversity of opinion is easily understood, the moment 

 we pass from natural facts to physiological speculations. 



The auditory nerve is distributed to every portion of the 

 labyrinth; but before entering it, while in the internal auditory 

 canal, it divides into two branches, the smaller one running 

 to the cochlea, and the larger to the vestibule and the semi- 

 circular canals. If we admit that the two branches are homo- 

 geneous, and only constitute two divisions of the auditory 

 nerve, we must conclude that the auditory impression is per- 

 ceived all over the labyrinth, just as the visual impression is 

 felt on every portion of the retina. The division of the 

 nerve, and the peculiar disposition of the ramifications in 

 each of the labyrinthine cavities, seem to indicate a special 

 function for each of these cavities. It seems natural to sup- 



