26 SYDNEY EVANS JOHNSON 



The nuclei of the columnar cells are small, round or elongated, 

 and are located at various levels in the cells. 



Cross sections show that for a short distance on each side of 

 the sensory ridge the colunmar epitheliuin is considerably modi- 

 fied and thickened where it o^•erlies rather large longitudinal 

 blood spaces (fig. 8). In many preparations some of the cells 

 in this region present full, rounded outlines, while others appear 

 greatly shrunken and vacuolated. The difference in appearance 

 of these cells under like treatment and their proximity to an 

 abundant blood supply suggests that they may have a secretory 

 function. 



The basilar membrane appears as a structureless sheet from 

 0.5 to 1 micron in thickness. It separates the sensory epithe- 

 lium from the longitudinal fiber zone, the blood capillaries and 

 other neighboring tissues. 



c. Peripheral terviinations of the nervus lateralis. Demonstra- 

 tion of the precise nature of the peripheral terminations of the 

 lateral nerve has been one of the most difficult tasks in connec- 

 tion ^\^th the study of the sense organs of the lateral canal sys- 

 tem. The earlier investigations on nerve terminations took 

 place before the introduction of silver impregnation, of methylen 

 blue, and of other modern methods. Retzius '92 and von 

 Lenhossek '92-'93 made numerous impregnations by Golgi 

 methods but they were unable to demonstrate the terminal 

 fibers of the lateral nerve. They expressed the belief, however, 

 that the nerve fibers ended, not in the hair cells, as Leydig 

 believed, but in free fibrillations in the sensory epithelium. 



Later investigators have held, largely, to the ideas expressed 

 by Retzius and von Lenhossek. Johnston '06 says that the 

 lateral nerve ends in complex fibrillations between the hair- 

 cells of the sense-organs. His statement, however, is based on a 

 brief unillustrated paper on the lateral sense organs of Ameiu- 

 rus by F. S. Bunker '97. Heilig '12 worked on the peripheral 

 terminations of the lateral nerve in a species of perch, but his 

 histological illustrations are not completely satisfactory. His 

 figures show the nerve fibers approaching the bases of the hair- 

 cells, but their relation to the cells is not shown. 



