The ^N'ature of the Tectorial j\Iembrane 139 



ings, "'pads,"' noted by Kolliker, "61, and more fully described by 

 Bottcher, '69, and Eickenbacher, '01. The lesser thickening is the first 

 indication of the differentiation of the organ of Corti, while the cells 

 of the greater give origin to the tectorial membrane and later gradu- 

 ally retract and sink back into the low, indifferent cells lining the spiral 

 sulcus. Bottcher thought that the tectorial membrane takes origin 

 from both the greater and the lesser thickenings. This can hardly be 

 claimed, for the pig, for while the edges of the two thickenings are, 

 of course, quite close together, the early membrane does not begin to 

 extend over the lesser till there are evidences of the beginning of retrac- 

 tion on the part of the greater thickening. Evidences to the contrary 

 of this are sometimes seen in the form of a thin, frayed reticulum 

 sticking to the inner edge of the lesser thickening and continuous with 

 the membrane, but serial study suggests that such appearances are due to 

 distortion and to coagulum films produced by the reagents. Two years 

 after its publication, Hensen showed that Bottcher's conclusion was 

 based in part upon artifacts. 



As Eickenbacher pointed out, the membrane, throughout its elabora- 

 tion, undergoes no active growth whatever, but is purely a passive 

 product of the continued activity of the epithelial cells below it. Not 

 till pigs of about 14 cm. do my preparations show evidences of differ- 

 entiation of the cells of the lesser thickening into what will become the 

 different cells of the organ of Corti (Fig. 10), and at that stage none 

 of the cells of the organ are in the least recognizable until traced back- 

 ward from the more advanced stages. The contention of Ayres, '91 

 and '98, partially supported by Czinner and Hammerschlag, '97, that 

 the tectorial membrane consists of a segregation of continuations of 

 the hairs of the hair cells of the organ of Corti. is shown in my prepara- 

 tions to be fully met by the statement of Eickenbacher, namely, that 

 the tectorial membrane is considerably developed some time before the 

 hair cells are differentiated as such. Eickenbacher showed further that 

 much of the findings of Czinner and Hammerschlag in this relation 

 were artifacts, and cites Hensen in suggesting the same to have been 

 true with Bottcher. 



By a process of retrogression and displacement, first suggested by 

 Kolliker and described later by Exner. '97. the tectorial membrane 

 developed wholly from cells at the inner side of the organ of Corti, 

 finally becomes so left that its outer part extends over the organ. At 

 first, when the lesser epithelial thickening is not apparent in the prepa- 



