40 IRVING HARDESTY 



used instead of that of another author, Hensen probably, for while only 

 in the passage of his paper incorporated by Prentiss does Ricken- 

 bacher state at all definitely that he considers a part of the tectorial 

 membrane proper developed from the lesser epithelial ridge, yet in 

 several places one may infer that he does o consider it. In the pas- 

 sage incorporated by Prentiss, the pa t in question is referred to as 

 follows: "Die schmale Randzone ist eine sekundare Bildung, welche 

 an dem kleinen Epithelial wulst ahgemndert wird." (Italics are mine). 

 In my paper, as stated, no attempt was made fo enter fully into the proc- 

 esses of development of the membrane. Sections from relatively 

 few early fetuses were examined. The purpose was to learn some- 

 thing of the nature of the membrane already developed. In the few 

 sections I had representing the stages of the differentiation of -the 

 spiral organ, the fibrils over the lesser ridge must have been exception- 

 ally sparse, for I considered them as artefact and omitted to show them 

 in the one figure offered dealing with development. Granular masses 

 and filaments are usually seen in the sections adhering upon other 

 parts of the epithelium lining the cochlear duct, especially in its angles, 

 and I described the fibrils I saw as a thin, frayed reticulum, sticking 

 upon the lesser ridge and continuous with the tectorial membrane, 

 composed of coagulum filaments resulting from the action of the fixing 

 fluid upon the endolymph. I considered Rickenbacher's pale staining 

 substance over the spiral organ as artefact, most especially his de- 

 tailed presentation of it in his figure 15, for in this he showed it as 

 adhering to the young spiral organ by five stout processes, four of 

 which each blended upon and surrounded only the hairs of the inner 

 and outer hair cells. Between these few attaching processes were 

 shown what were evidently shrinkage spaces, though he called them 

 'intercommunicating spaces in which the endolymph circulates.' 

 He called the processes 'fiber bundles,' which was perhaps true, but 

 the predominant structure of his mass appeared to be granular and I 

 considered it artefact, as it was, especially the arrangement of his fiber 

 bundles. In the present study, I cannot agree for the pig with any 

 of his interpretations of his Deckschicht. I agree with him that the 

 tectorial membrane becomes free from the spiral organ. 



Up to pigs of about 16 cm., the greater epithelial ridge grows 

 thicker and wider and the activity with which the membrane 

 is produced by it increases. The outer third of the greater ridge 

 becomes thicker than the axial two-thirds, the position of its 

 nuclei giving the impression that its long cylindrical cells have been 

 forced apexward by growth pressure. Figure 7, from the 3rd 

 half turn of a pig of 14 cm., shows this but to a less extent than 

 may occur at IG cm. The rapidly growing, outspanning zone 

 of the tectorial membrane coincides with the surface of the 



