



VIEW OF THEIR ANATOMY AND DEVELOPMENT. 130 



vesicles; and hence, if we are disposed to follow the statements 

 of Remak, we must refer their origin to the horny lamina of 

 the embryo, by the inversion of which into the matrix of the 

 fibrous portion of the temporal bone these vesicles arise. The 

 traces of this involution betray themselves, as Bottcher (3) has 

 recently shown, in the epithelial investment of the aquoeductus 

 vestibuli, still present in adults (recessus labyrinthi of Reissner) 

 which in the Plagiostomi actually opens by a fine pore on the 

 surface of the skin. Strieker (64), Schenk (63), and Torok (65), 

 have demonstrated in the case of the Batrachia, that it is not 

 so much the horny lamina as the immediately subjacent layer, 

 termed by Strieker the " sensorial layer," the involution of 

 which leads to the formation of the auditory labyrinth, a state- 

 ment that has recently been corroborated by van Bambeke (58). 

 In this case there would be complete harmony in the mode of 

 development between the labyrinth and the retina, as well 

 as the olfactory vesicle, all of which parts, together with the 

 central nervous system, must be referred to the sensory layer. 

 As Kolliker has pointed out, the organ of Corti, the most 

 essential constituent of the cochlea, is developed from the 

 involuted epithelium of the ductus cochlearis, and I shall 

 recur to the most remarkable details of this process, so far as 

 they are at present known, in the course of my description of 

 that part. 



In the above rude outline of the comparative anatomy and 

 developmental history of the cochlea, we obtain the general 

 ideas requisite for the right comprehension of its histology. 



cushion coalesce ; L Sp, ligamentum spirale of Henle ; L Sp a, liga- 

 mentum spirale accessorium, with the vas prominens ; S sp e, sulcus 

 spiralis externus ; E E h Reissner's membrane, the two ends being 

 alone preserved ; R Or, crista spiralis ; Cr, its most prominent 

 portion (auditory teeth) in transverse section ; Mt, membrana tec- 

 toria ; 8 sp i, sulcus spiralis internus ; /, point where the nerves 

 traverse the lamina spiralis (habenula perforata) ; / L Sp, mem- 

 brana basilaris ; / p, Corti's organ ; Or p, zona denticulata ; y h, 

 zona arcuata ; p L Sp, zona pectinata, with epithelium ; </, region 

 of the internal hair cells (internal portion or slope of the roof, innere 

 Abdachung) ; I, thinnest part of the membrana basilaris beneath the 

 arches of Corti ; h, region of the external hair cells (external portion 

 or slope of the roof, aussere Abdachung). 



