No. I.] THE VERTEBRATE EAR. IC)^ 



cells. The sixth cell of the small ridge develops in the fourth 

 row of outer hair cells. 



Gottstein, however, concluded that in the Dog the last cell 

 of the large ridge developed into the inner hair cell, and that 

 the nerve fibres, which enter the habenula perforata, must neces- 

 sarily force their way upward through the cells of this ridge, 

 since they cover over the openings. The nerve fibres become 

 connected with the cells of the large ridge which undergo 

 atrophy, and later on are reduced to the so-called granular cells 

 (Kornershicht, Gottstein). 



The sulcus internus arises by the growth of the basilar mem- 

 brane between the inner edge of the large ridge and of the 

 crista spirahs, and not alone by the disappearance of the mass 

 of the ridge itself, as Boettcher believed. 



The cells forming the acoustic apparatus outside the outer hair 

 cells in Man, Boettcher supposed were derived from the zona 

 pectinata. Hensen called them supporting cells, while Gottstein 

 was inclined to look upon them as being the remaining cells of 

 the small ridge which had not reached a full development. He 

 speaks of three rows of hair cells for mammals other than Man, 

 and of four rows for Man as developing out of these cells. 

 The evidences which led him to this conclusion were the simi- 

 larity in the rounding off of the embryonic and adult ridges, 

 and the presence in Man of a greater number of rows of hair 

 cells than is present in most mammals (the latter statement 

 has been shown by Retzius to be incorrect, and as my own 

 preparations show, the Pig, Cat, Ox, and Man have equally 

 the four, and even five, rows of hair cells of the external group), 

 and the presence along the outer border of the membrana reticu- 

 laris of additional elements beyond the region of the hair cells. 



The inner hair cells were first well figured by Deiters, but 

 Boettcher claims to have discovered them. He says (Joe. cit. 

 p. 94) with reference to the hairs borne by these cells : " Wie 

 aus meinen Untersuchungen hervorgeht sind die Haare oder 

 Stabchen, welche an der Oberflache sowohl dieser innern, als 

 auch der spater zu nennenden aussern Haar-oder Stabchenzellen 

 an vielen Praparaten sichtbar sind, kiinstlich durch Abreissen 

 der Corti'schen Membran erzeugt. Ich habe mich daher aus 

 diesem Grunde veranlasst gesehen beide Namen zu verwerfen." 



According to Boettcher, the hair cells at first are simple, but 



