662 MANUAL OF HISTOLOGY. 



The form of the external pillar is allied to that of the internal, although, 

 by no means quite the same. A glance at fig. 608 will render any further 

 description unnecessary. 



These remarkable structures are composed of a transparent homoge- 

 neous substance, offering but slight resistance, however, to the action of 

 reagents. 



But the cellular elements of the organ of Corti are no less remarkable. 



Commencing from within from the sulcus spiralis, we may observe that 

 the epithelial cells become higher, so that at about the middle of the 

 internal pillars of Corti a high ridge of epithelium (g) is formed. Here, 

 then, we come upon a peculiar structure, known as the internal " hair cell" 

 or tufted cell of Deiters. We shall frequently have occasion again to refer 

 to the cells in question, which, taken all together, naturally form a spiral 

 row. 



Now, just as the internal hair cell lies in a slanting direction upon the 

 internal pillar covering it, so do the external hair or tufted cells or cells of 

 Corti of earlier observers (p, q, ?), of which there are three or four rows, 

 cover the external pillars, similarly inclined. They are said, however, 

 by the most recent observers (Gottstein and Waldeyer) to be double cells, 

 and the pillars of Corti are, probably, also developed from such twin 

 cells likewise. 



External to the outer hair-cell spiral we next come upon columnar 

 epithelial elements, the so-called " supporting cells " of Hensen (fig. 608, 

 z; 607, r). Beyond this, the latter become shorter and shorter, until 

 they gradually merge into the simple cubical epithelium of the zona 

 pectinata (fig. 606, k). 



Let us now bestow a glance upon that wonderful fenestrated covering 

 membrane, known as the lamina reticularis of Koellilcer or I. velamentosa 

 of Defers, essential to our gaining a comprehensive idea of the whole. 



In fig. 608 the position of this covering membrane is represented in 

 side view from I to l' f but its remarkable structure can only bo recognised 

 from above, as in fig. 607. 



From as far inwards as the internal pillars, the epithelial cells give 

 off a cuticular annular limiting border (c). Above this, then, the internal 

 hair-cells (e) reach the same height as the organ of Corti. 



Each internal pillar of the latter, then, is prolonged into a pretty broad 

 horizontal plate, which rests upon the top of an external pillar. In fig. 

 607 these internal "head plates" are represented at/, i. Beneath them 

 lie the head plates of the external pillars, likewise horizontal (607, I ; 

 608, m). These plates have a long narrow neck, and present an oar- 

 shaped figure. They constitute the first phalanges of the lamina reti- 

 cularis. In these head plates the latter cuticular formation has its 

 commencement. 



A glance at fig. 607 will convey a more rapid idea of the annulary con- 

 dition of this lamina reticularis than any description, however minute 

 (k, m, o). With the first phalanx we are already acquainted. At n and 

 p, the second and third rows of phalanges are to be seen. K, m, o, indi- 

 cate the tufts of hairs of the three spiral ranks of the so-called external 

 hair cells. Finally, at E, descending again, we come upon the external 

 epithelial cells of the tnembrana basilaris. But between these also 

 further prolongation of this cuticular mesh-work may be recognised. 

 This is the so-called "terminal frameivork" of Deiters (q). 



The zona pectinata (fig. 606, g), i.e., the external portion of the lam. 



