THE EAR. 



363 



The scala tympani is a blind canal, having at one extremity 

 the membrane which covers the fenestra rotunda, and at the 

 upper part terminating in the cupula of the cochlea, where it 



s 



Lsp 



FIG. 162. Section of the cochlea of a human embryo at the fourth month, a, a, a, cartilaginous 

 incasement of the cochlea ; ft. 6, perichondrium ; c, mucoid tissue matrix of the modiolus ; d, d, cartila- 

 ginous septa of the individual turns of the cochlea ; e c 4 , sections of the ductus cochlearis ; /, f^ Reise- 

 ner's membrane ; #, membrana tectoria. somewhat lifted up from the subjacent parts ; h. rudiment of the 

 stria vascularis ; t, rudiment of the subsequent organ of Corti ; L *p, lamina spiralis ; Gl, Gl, ganglion 

 spirale with various efferent and afferent bundles of nerves ; /ST, scala tympani ; SV, scala vesfibuli ; 

 ST lt SV lt /Sr 2 , muccid tissue where later the scalae of the last cochleal turn will be. 10, Waldeyer. 



is said to enter into communication with the scala vestibuli 

 by a minute opening, the helicotrema. 



The scala vestibuli stands in direct communication with the, 

 perilymphatic space of the vestibular sacs, while the ductus 

 cochlearis is in communication with the saccule by means of 

 a slender canal (the canalis reuniens). The walls of the two 

 scalse are formed of a thin periosteum, on the surface of which 



