ORGANS OF SENSE. 183 



bula, and cochlea, are covered by a layer of connect- 

 ing tissue, with pavement epithelium upon its surface. 



The walls of the membranous labyrinth consist of 

 a lamina of extremely delicate connecting tissue, the 

 fibrillated character of which is with difficulty recog- 

 nizable, but it contains a large quantity of oval (fibro- 

 plastic) nuclei, and is covered by a very thin amor- 

 phous layer, on the internal surface of which we find 

 a stratum of pavement epithelium. 



The white specks which are observed upon the 

 inner surfaces of the sacculus communis and sacculus 

 proprius (otoliths, otoconites) are composed of cal- 

 careous granules, which sometimes present a crystal- 

 line aspect. Both outside and inside of the tubes 

 and cavities forming the membranous labyrinth, is a 

 pellucid fluid (pe.rilymph, endolymph), the chemical 

 nature of which is not as yet clearly determined. 



The nerves which reach the ampullae of the semi- 

 circular canals and the sacculi appear to terminate 

 by free extremities, after having undergone frequent 

 division and subdivision ; beyond these localities it 

 has been found impossible to trace them. 



The vessels form a close network which principally 

 occupies the fibrous coat of the semicircular canals, 

 and the two vestibular sacculi. 



The labors of Corti* and Kolliker tend to prove 

 that the nervous fibres of the cochlea terminate by 

 free extremities in the substance of the membranous 

 portion of the lamina spiralis. These authors have 

 also demonstrated that there are cellular enlarge- 



* Corti wrote on the structure of the retina in Miiller's Archiv, 1850, 

 p. 274. (Ed.} 



