102 THE MEMBRANOUS LABYRINTH, BY PROF. RUDINGER. 



These form a regular tesselated epithelium upon the inner 

 surface of the basement membrane on which they rest. A 

 larger form of epithelium occurs on the thicker part of the 

 canal wall ; but to a limited extent only ; the appearance pre- 

 sented being as though the peculiar columnar epithelial cells 

 of the utriculus and of the ampullae, which form a narrow stria 

 opposite to the nerve epithelium, and which have been minutely 

 described by Hasse under the name of roof -cells (Dach-zellen) } 

 were also continued into the semicircular canals. 



Figr. 306. 



Fig. 306. Sagittal semicircular canal of the Pigeon. 1, Groove 011 

 the thick portion of the canal for the reception of a vessel ; 2, thinner 

 portion of the wall ; 3, cartilage of the labyrinth traversed by large 

 vessels ; 4, pavement epithelium. Magnified 170 diameters. 



The proportionately thick- walled semicircular canals of the 

 Fish * vary in their thickness and in the shape of their lumina 

 in the different families. In the Pike (fig. 307) the canal is 

 triangular on transverse section, with a thick basal segment 

 (corresponding to the thick free portion of the wall), and 

 two lateral portions which, gradually becoming thinner, join in 

 an arcuate manner. The part which is adherent to the bony 



* My own investigations have been limited to the families of the 

 Perch, Carp, Salmon, and Pike. 



