▼■] 



THE MEMBRANOUS LABYRINTH. 



113 



goes to form the epithelium of the membranous labyrinth, 

 whose curiously twisted cavity rilled with endolymph repre- 

 sents the original cavity which was first open to the surface 

 but subsequently covered in. The corium of the mem- 

 branous labyrinth, and all the tissues of the osseous labyrinth, 



Fig. 34. 



cc 



Transverse Section of the Head of a Fcetal Sheep (16 mm. in length) 

 in the region of the Hind Brain. (Copied from Boettcher, Enticicke- 

 lung und Bau des Gehorlabyrintlis.) 



This figure, together with Figs. 33 and 34, though referring to mammalian 

 structures, are introduced here, in order to illustrate the account given in the 

 text. 

 H.B. the hind brain, the lines of reference starting on both sides from the 



greatly thickened side walls. 



The section is somewhat oblique, hence while on the right side the connec- 

 tions of the recessus vestibuli, R.L., and of the commencing vertical semicircular 

 canal Y.B. and of the ductus cochlearis C. C, with the cavity of the primary 

 otic vesicle are well seen, on the left side, only the extreme end of the ductus 

 cochlearis C.C. and of the semicircular canal Y.B. are shewn. In the same way 

 the cavity of the throat appears from the obliquity of the section to be one-sided. 



Lying close to the inner side of the otic vesicle is seen the cochlear 

 ganglion G. C. ; on the left side the auditory nerve G and its connection N with 

 the hind-brain are also shewn. 



Below the otic vesicle on either side lies the cardinal vein. 



E. 



8 



