104 THE MEMBRANOUS LABYRINTH, BY PROF. RUDINGER. 



membrane of the inner surface, composed of moderately large 

 cells with well-defined nuclei, which, when seen in profile, are 

 fusiform. In the Pike there is a much broader band than else- 

 where, situated on the thick side of the canal, and composed 

 of columnar cells. In no animals do the epithelial cells with 

 their basement membrane separate so easily as in Fishes ; the 

 whole lamella becoming detached, and appearing as a smaller 

 canal on transverse section, which may be adherent to some 

 point of the cartilage wall. Frequent examination leads, how- 

 ever, to the conclusion that this is the result of manipulation, 

 and is due to the loose connection of the epithelium with the 

 tunica propria. 



In the year 1844, A. Ecker described the presence of ciliated 

 epithelial cells in the semicircular canals of Petromyzon mari- 

 nus, which, however, as H. Reich, a pupil of Ecker's, observed 

 in 1857, in the Ammocoetes, really belong only to the crista 

 acustica or macula acustica, and not to the semicircular canals. 



I have observed a peculiar isolated structure in the mem- 

 branous labyrinth of Salmo huclw (fig. 308). In the adjoining 

 figure it may be seen that the wall and the lumen of the canal 

 in this fish present many points of difference from that of the 

 Pike. The thick portion of the external wall of the canal is 

 unevenly divided by a groove on its external surface, and the 

 hyaline matrix is present in much larger proportion in rela- 

 tion to the connective-tissue corpuscles. 



Arising from the thick portion of the wall are two rows of 

 cells, with an interval between them. They form, as it were, 

 the two walls of a groove, and project to a moderate distance 

 into the canal. (See fig. 308.) These extend along the whole 

 length of the canal, with this difference only, that their height 

 diminishes towards the utriculus. 



From beneath the epithelial cells situated at the margin 

 of each wall, very delicate pale fibres project, which are 

 surrounded at their origins by protoplasm, undergo dichoto- 

 mous division, and are connected with rounded or oval cells 

 like grapes on their stalks. The whole row of cells which is 

 thus formed floats to a certain extent in the endolymph of the 

 semicircular canal. Surface views show that both cell rows 

 extend at definite distances towards each other, so that as it 



