Sz AY'ERS. [Vol. VI. 



Mammalia an epitome of their phylogenetic history, and in the 

 embryo mammal we may recognize the reptilian condition as 

 illustrated in the organ of Corti of the Alligator ear. These 

 cells appear to be well formed and separate the first two rows 

 of hair cells, but they do not possess such marked fibrous struc- 

 tures as are present in the mammalian pillar cells. The blood- 

 vessel which runs below the floor of the organ (formed by the 

 basilar membrane) is present practically as in the mammalian 

 ear. 



Connected with the pillars of Corti and forming a part of its 

 supporting framework is a structure formed by the cell caps of 

 the supporting cells on either side of the pillar row, and which, 

 from its appearance when isolated, has been called very appro- 

 priately the membrana reticularis. 



I am confident that the reticular structure is a product merely 

 of the cell caps of the supporting cells,^ and that the intercellu- 

 lar substance, if such exist, is not important in the formation of 

 its framework. The hair cells are only lightly attached to the 

 supporting cells. Everywhere except in the region of the 

 reticulate membrane they are separated, in fact, by considerable 

 interspace, but in this region the cell caps of the hair cells seem 

 to fill interspaces or the reticula of the membrane ; and since 

 the tops of all the cells of the organ lie close together and form 

 a mosaic, and since the supporting cells adhere very tenaciously 

 to one another by their cell caps, it is very easily understood 

 how the structure may appear as a discrete structure, after the 

 organ of Corti has been passed through the processes of pres- 

 ervation, hardening, staining, clearing, dissecting, and mounting, 

 one or all, before observation. 



The membrane has no individual existence any more than the 

 membrana tectoria, and with this we have removed another feat- 

 ure of the cochlear anatomy, which appeared to show a want 

 of harmony between the type anatomy of the canal organ and 

 that of the highly modified Corti's organ. 



1 The reticulate membrane very frequently retains the cell caps of the hair cells 

 within its meshes, but under the definition they are not to be considered constituents of 

 this structure. From the new standpoint they are on the same footing with the isola- 

 tion cells as contributors to the reticulate frame. That the hair cells are less firmly 

 fixed by their upper ends is apparent from the greater ease with which they separate 

 from the membrane. 



