446 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



tympanum just below the fenestra ovalis, and the 

 scala vestibuli leads to the perilymphatic space of 

 the vestibule. The fenestra rotunda is closed by 

 the tympanic membrane. 



From what has been stated it is evident that an 

 injection into the scala tympani through the fora- 

 men rotunda will pass into the scala vestibuli at the 

 apex of the cochlea, and travel down the passage 

 above the lamina spiralis to ultimately reach the 

 perilymphatic space of the vestibule and exert press- 

 ure against the base of the stapes through the fenes- 

 tra ovalis. 



The membranous cochlea (ductus cochlearis or scala 

 media) forms a spiral canal inside the bony cochlea, 

 and ends at the apex of the latter in a blind ex- 

 tremity, the lagena. This scala media lies near the 

 free margin of the lamina spiralis and just above 

 the membrana basilaris. It thus forms a spiral tube 

 that gradually increases in size from its lower to its 

 upper or distal end. Its lower end communicates 

 with the sacculus through the ductus reuniens of 

 Hensen. Triangular in transverse section it has a 

 roof, called Reissner's membrane, which separates it 

 from the scala vestibuli. Its outer wall is the peri- 

 osteal lining of the bony cochlea, while its floor is the 

 outer border of the lamina spiralis and the membrana 

 basilaris. This membranous labyrinth is clothed 

 throughout its whole length by a single layer of 

 epithelial cells. 



Reissner's membrane consists of an exceedingly 

 thin connective-tissue lamella lined on the vestibular 

 side with a single layer of endothelial cells, and on the 



