122 Irving Hardesty 



Dupnis, '94:, and others have described the inner edge as sometimes 

 notched. Xotches were frequently seen in my preparations, but they 

 were always angular and could be explained as breaks suffered in freeing 

 the membrane from its attachment. 



The outer edge of the tectorial membrane in all my preparations is 

 rounded and terminates bruskly. In discussing observations made by 

 Kolliker in 1859 which denied an attachment of the outer edge of th'e 

 membrane to the lamina reticularis and the cells of Hensen of the 

 organ of Corti, Lowenburg, '64, described a delicate, almost invisible, 

 seemingly frayed-out reticulum along the outer edge. Others have since 

 mentioned this appearance, giving it the name, Loicenherg's border 

 plexus. Dupuis, while admitting that it is very irregular, usually 

 appearing in fragments, and not always present, referred to it as a 

 third and outermost zone of the tectorial membrane, while A^on Ebner, 

 '02, among others, refers to it as a filamentous structure, adhering to and 

 collapsed upon the outer zone of the membrane and representing its 

 original connection with- the lamina reticularis. 



The existence of this border plexus as a normal appearance of the 

 tectorial membrane is here denied. 



Though the appearance observed may be seen at times in the prepa- 

 rations used here, there is evidence that it may be due to three causes, 

 separately or in conjunction: First, it has always been observed in 

 fixed preparations, and the fixing fluids and especially the alcohol 

 produce coagulation of the albumens and globulins in the endolymph, 

 Coagulum filaments, in forming, always appear most abundant on 

 surfaces, and especially between surfaces which are close together. The 

 places on the tectorial membrane where these filaments are most apt to 

 be noticed are its outer edge and that portion of its under surface 

 which is imposed upon the organ of Corti. Second, evidences of 

 beginning liquefaction of the matrix of the membrane are, in the 

 preparations used here, always most apparent along its outer edge and 

 under surface. Portions of the fibers in the membrane, set free along 

 the edge by the dissolution of the matrix, may produce a delicate, 

 tangled, filamentous appearance which is no doubt augmented by 

 coagulum filaments produced by the reagents. Third, in the study of 

 the removed pieces of the tectorial membrane, I have now and then 

 seen what appeared to be parts of Lowenberg's border plexus, but these 

 appearances proved to be displaced portions of the accessory tectorial 

 membrane described below (Figs. 3 and 5). In the region of the basal 



