DEVELOPMENT OF THE ORGAN 



brane is supported by the tympanic ri 

 which have already been dealt with (p. 

 arteries of the first cleft supply the drum 

 The Membranous Labyrinth. Origi 

 tain area of epiblast, situated above the 

 37), become ultimately sensitive to soun 

 invaginated during the third week, and 

 pyriform sac, the otocyst, which lies abov 

 in the mesoblastic tissue between the hinc 

 (Figs. 37 and 39). The sac contains a fli 

 also otoliths are found in it later. The 



ductus endolymph. 



from primit 

 scala media 



cochlear canal 



Fig. 44. — Diagram of the Membranous : 



coat of mesoblast. The epithelial cells Hi 

 originally columnar, soon become flattened 

 acousticae, where they retain the colum: 

 hair-like processes. These become connect 

 by the auditory nerve fibres of the cochlea] 

 In the lower vertebrates, as in the ear] 

 the higher mammals, the otocyst is of a 



