No. I.] THE VERTEBRATE EAR. m 



When, however, we review the history of the controversy of 

 the nature of the cupula terminalis and the gelatinous mass 

 said to inclose the otoliths of the macula utriculi and macula 

 sacculi, we find that the older view, according to which these 

 structures were constant and normal organs of the internal 

 ear, was forced to give way to the demonstration of their arti- 

 ficial nature brought by Hensen, and when we consider the 

 view which I have endeavored to establish, viz. that the cochlear 

 organ of the mammalian ear is morphologically but a trans- 

 formed row of lateral line sense organs, each of which inherits 

 the capacity to produce a structure in every way like the cupula 

 terminalis, and when we examine the minute structure and rela- 

 tion of the parts of the meinbrana tectoria in this connection, 

 I feel confident that it will be apparent to every one that the 

 membrana tectoria of the mammalian ear is but a cupula termi- 

 nalis-like structure produced by the gluing together of the 

 hairs of the sensory cells of the organ of Corti and the break- 

 ing away of the whole from the cells which bear them, as in the 

 case of the cupula hairs. This membrana tectoria, as it is found 

 in ordinary microscopical preparations of the mammalian cochlea, 

 is, then, an artifact produced by the use of reagents. In his 

 later studies Retzius was converted to Hensen's view of the 

 cupulae terminales, and recognized two very definite forms in 

 his own preparations which he called the osmium and Mullerian 

 cupulas respectively, since he was satisfied their peculiarities 

 and distinguishing characters were due entirely to the re- 

 agents used. The effect of the following reagents are the only 

 ones I have specially noted during my work, but any one who 

 will test the matter and compare his results with the published 

 figures will find the influence of reagents distinctly marked 

 in the conceptions of the nature and relations of the mem- 

 brana tectoria. 



Hydrochloric acid swells the hairs, causing them to fuse and 

 the boundaries to disappear. It shortens the length of the 

 hairs correspondingly, so that in transverse sections the mem- 

 brane is usually homogeneous and club-shaped when this re- 

 agent is used. 



Nitric acid acts much in the same way as the hydrochloric, 

 though it contracts the hairs much more strongly. This is 

 especially true of the higher per cents (10-20) used in decal- 



