The jSTature of the Tectorial Membrane 133 



coil^ the outer edge of this accessor}^ membrane nearly coincides with 

 the outer edge of the main body of the tectorial membrane;, and but 

 slight displacements will result in its projecting far enough to be 

 separately distinguished. 



Corti, in first describing the tectorial membrane, expressed the belief 

 that the outer edge was normally attached to the structures below it 

 and located this attachment as far over as the epithelium upon the 

 spiral ligament. Coyne and Cannieu, '85, agreed with Corti in so far 

 as to place the attachment upon the cells of Claudius, and ever since 

 Corti, investigators have looked for and claimed an attachment of the 

 outer edge, though seldom agreeing as to the locality, and they have 

 explained Lowenberg's Iwrder plexus as the outer edge of the membrane 

 frayed by having been torn from its attachment. Quite recently, Kishi, 

 '07, Avho seems to believe that the membrane is normally attached to 

 the organ of Corti, states that* the border plexus, or third zone, is only 

 an artifact which results from the tearing of the membrane from the 

 organ of Corti, and which consists either of the frayed edge of the 

 membrane alone, or of this edge together with a portion of the lamina 

 reticularis removed with it. On the other hand, l^eginning with 

 Hensen, '63, and Bottcher, '72, the outer attachment has been frequently 

 denied. Kolliker and Yon Ebner admit, from the study of its develop- 

 ment, that at one time the tectorial membrane is of necessity attached 

 along its under surface, but that early, during the differentiation and 

 elaboration of the organ of Corti, and the resultant displacement and 

 adjustment, the attachment of the outer edge at least becomes obliter- 

 ated. Ferre, '85, described the outer edge as bluntly rounded, and so 

 it appears in the large majority of preparations, in both sections of 

 fixed cochleae, always allowing for shrinkage, and also in the fresh con- 

 dition in teased preparations. 



Measurements of the ividth of the tectorial membrane of the pig 

 were carefully taken at the different turns of the coil of the nine teased 

 preparations obtained. These measurements were transversely across 

 each tip or extremity and across the intervening portions at intervals 

 of each half turn of the coil. IsTow and then partial breaks or slight 

 distortions appeared in short portions of a specimen, and if these appeared 

 in the particular portion of the turn to be measured and seemed suffi- 

 ciently serious to invalidate the measurement, the measurement for that 

 interval had to be omitted. However, these injured places were not very 

 numerous, and, from the nine specimens, enough trustworthy measure- 



