70 



DEVELOPMENT OF THE ORGANS OF SENSE. 

 Fig. 572. 



Fig. 572. — Transverse Section of the Head op a Fcetal Sheep of four-fifths of 

 AN INCH IN LENGTH (from Foster and Balfour after Boettclier). 



RV, recessus vestibuli ; VB, vertical semicircular canal ; CC, cochlear canal ; G, 

 cochlear ganglion ; HB, horizontal canal. 



Fi-. 573. 



Fig. 573. — Tr.ANsvERSE Section of 

 THE Cochlea in a Fcetal Calf, 

 magnified (from Kolliker). 



C, the wall of the cochlea, still 

 cartilaginous ; c c, canalis cochlear ; 

 I s, placed in the tissue occupying the 

 place of the scala vestibuli, indicates 

 the lamina spiralis ; n, the central 

 cochlear nerve ; (/, the jjlace of the 

 spiral ganglion ; S, the body of the 

 sphenoid • ch, remains of chorda dor- 

 salis. 



the epiblast, and an outer car- 

 tilaginous or bony and fibrous 

 wall, together with other ad- 

 ventitious structures arising- 

 in the mesoblast. 

 Labyrinth. — In the development of the primary otic vesicle after 

 it becomes completely closed, a series of very remarkable changes by 

 extension of its cavity in different directions gives rise to the formation 

 of the different parts of the labyrinth. The first complication which 



