THE INTERNAL EAR IN VERTEBRATES 575 



it is essential to have a working plan of the form and relative 

 positions of the different parts of the finished product to which 

 the evolutionary process has eventually led. Such a plan is 

 presented in fig. i, in which the chief parts of the left internal 



RlOR CANAL 



■EXTERNAL AMPULLA 

 ANTERIOR AMPULLA 



STRIA N*SCUl.ARI&- 



LIC SPIRALE 



Fig. i. — Left membranous labyrinth of man, seen from the mesial aspect. 



The endolymph labyrinth has been left white, the cavities of the perilymph labyrinth dotted. A section is 

 supposed to have been cut out of the cochlea, to show the arrangement of the three cavities, scala 

 media or cochlear canal, scala vestibuli, scala tympani. (Based on Schoenemann.) 



labyrinth of man are shown diagrammatically from the mesial 

 aspect. The diagram is based on the figures in Schoenemann's 

 atlas checked by a preparation of the human membranous 

 labyrinth made by Dr. Albert Gray and now in the Museum of 

 the College of Surgeons and by sundry preparations of the 

 37 



