108 THE MEMBRANOUS LABYRINTH, BY PROF. RUDINGER. 



given off both towards the periosteum and towards the free 

 wall of the membranous canals and the ligamenta labyrinth! 

 canaliculorum ; from whence, surrounded by a few fibres of con- 

 nective tissue, they return as veins. The arteries and veins 

 do not lie in close contiguity in the osseous canals, and it is 

 frequently very difficult to distinguish them from each other, 

 or from the thick-walled capillaries (fig. 297). 



Towards the vestibule the two vessels become approximated, 

 although it is still doubtful whether the veins follow the course 

 of the branches given off by the arteria auditiva interna. 



Transverse sections through the aquseductus vestibuli de- 

 monstrate that large vessels run close to this serous passage, 

 which, from their external characters, appear to be veins, and 

 which have already been described by Hyrtl as the veins of 

 the vestibule. 



4. NERVES AND EPITHELIUM OF THE AMPULLA AND SACCULI. 



Corresponding with the region of the distribution of the audi- 

 tory nerve in the sacculi and ampullae of the various classes 

 of animals, the internal surface constantly presents a peculiar 

 form of epithelium, for the most part containing yellowish pig- 

 ment, and beset with firm cilia ; so that, from the constant co- 

 incidence on the opposite sides of the membrane of the above- 

 mentioned morphological elements, we may draw the conclusion 

 that they are necessarily associated together. For the study of 

 the topographical and histological characters of the nerves and 

 their relations to the epithelium of the ampullae and sacculi, 

 fresh sections made in various directions through specimens 

 that have been decalcified and hardened in chromic acid, and 

 those also which, after being made, have been allowed to imbibe 

 various fluids, and have been further divided, are best adapted.* 



After attention had been directed by Scarpa and E. H. 

 Weber to the mound-like process (called " septum " by Scarpa) 



* I find of especial value that mode of imbibition which proceeds under 

 the eye of the observer. To this end I lay transverse sections of the 

 ampullae with the nerves upon a slide, and add a few drops of perosmic 

 acid, watching at the same time its gradually increasing action on the 

 nerves and epithelium. 



