48 IRVING HARDESTY 



the end of each cell, similar to the way cilia often appear in 

 brushes in sections of the uterine tube and the ducts of the 

 testis, for example. When shrinkage and agglutination are 

 less evident than in figure 11, the bundles are smaller and may 

 be formed indiiferentlj^ upon and between the ends of the cells. 

 When more shrinkage has occurred the bundles may be larger 

 and the shrinkage spaces may extend over several cells. The 

 spaces are similar to those Rickenbacher pictured and considered 

 as designed for the circulation of endolymph. Figures 10 and 

 11 are not camera drawings. 



The attachment and functional position of the tectorial mem- 

 brane are interrelated. The outspanning zone, after it is pro- 

 duced, becomes entirely free, first from its slight attachment to 

 the young spu-al organ (lesser epitheUal ridge) and later from its 

 parent cells, and the process by which it becomes free is the chief 

 of the processes by which it later attains its functional position 

 over the spiral organ. Held ('09) quite fully reviewed the 

 ideas advanced by the different authors as to how the auditory 

 hair cells, developed in the lesser ridge at the outer edge of the 

 growing membrane, acquire their much more axial position well 

 under the membrane, and I cited most of them in my former 

 paper. I think all the processes possible have been suggested. 

 When the younger stages are compared with the stages after 

 birth (compare figures 7 and 8 with figure 2) it is seen that the 

 spiral organ may become so shifted in its relative position that 

 its hair cells come to stand under the middle of the basal sur- 

 face of the outspanning zone of the membrane, and that the 

 outer edge of the membrane may project in the 3rd half turn 

 (and no doubt more in the 1st) well beyond the organ and even 

 over the first 10 or 12 of the cells of Claudius. Under the nar- 

 row basal end of the membrane (fig. 4), the shifting of position 

 is barely sufficient to bring the outer edge over the outer 

 hair cells of the organ. In this region the greater epithelial 

 ridge completes the membrane earlier, is active during a shorter 

 period, and increases in width during production much less than in 

 the apical turns. It may be noted further that in the more apical 

 turns the outer supporting cells increase in height so much more 



