584 



THE ORGANS 



crosses the space intervening between the spiral ligament and the 

 bony spiral lamina,, thus completely dividing the bony canal of the 

 cochlea into two parts, an upper, scala vestihuli (Fig. 389, /) and a 

 lower, scala tympani (Fig. 389, k). These are perilymphatic spaces, 

 the scala vestibuli communicating with the perilymph space of the 

 vestibule, the scala tympani communicating with the perivascular 





1 '•" . 1 1 ' 



ttl 



v^'/v^-;^ 



■^ \?; 





& 









Fig. 389. — Section through a Single Turn of the Cochlea of a Guinea-pig. (Bohm 

 and von Davidoff.) a, Bone of cochlea; I, scala vestibuli, Dc, scala media or cochlear 

 duct; k, scala tympani; 6, membrane of Reissner; c?,membrana tectoria or membrane of 

 Corti;/, spiral prominence; g, organ of Corti; //. spiral ligament; i, basilar membrane 

 (outer portion — zona pectinata— covered by cells of Claudius); 2, stria vascularis; v, 

 external spiral sulcus; r, crista basilaris; s, membranous spiral lamina; x, bony spiral 

 lamina; m, spiral limbus; n, internal spiral sulcus; 0, medullated peripheral processes 

 (dendrites) of cells of spiral ganglion passing to the organ of Corti; />, spiral ganglion; 

 q, blood-vessel. 



lymph spaces of the veins of the cochlear duct. The scala vestibuli 

 and the scala tympani communicate with each other in the cupola by 

 means of a minute canal, the helicotrema. 



The Cochlear Duct {Membranous Cochlea or Scala Media). — 

 This is a narrow, membranous tube lying near the middle of the 

 bony cochlear canal and following its spiral turns from the vestibule, 

 where it is connected with the saccule through the canalis reuniens. 



