On the Perilympliatic Spaces of the Aiii])liibian Ear. 257 



with tlie exterior thus obtained by the membranous labyrinth 

 were adyantageous, and that the retardation culminated in sup- 

 pression. 

 f) The theory affords us a common explanation for the existence 

 of all the perilymphatic apertures, and for their relations to the 

 spaces. 



10. Considerations associated with the above theory as to the 

 origin of the fenestra vestibuli, support the view that the operculum 

 is a derivative of an element originally foreign to the auditory capsule. 



Cardiff, December 1901. 



Internationale Monatsschrift für Anat. ii. Phys. XIX. 17 



