GROWTH OF THE INNER EAR OF ALBINO EAT 27 



is not yet to be seen. Deiters' cells become longer, somewhat 

 in the processus phalangeus but chiefly in the cell body, and the 

 nuclei move upward. Hensen's cells also increase in height 

 slightly. 



While the membrana tectoria lies close to the surface of the 

 outer part of the greater ridge in the upper turns of the cochlea, 

 there arises a small space between them, which is continuous with 

 the sulcus spiralis internus. The outer marginal zone of the 

 membrane is still connected with Hensen's supporting cells and 

 the lamina reticularis. The vas spirale remains as a large vessel. 

 This is the condition of the nine-day cochlea in a rat which does 

 not hear. 



Although the detailed description of the cochlea of the nine- 

 day rat which can hear will be deferred for a time, yet to complete 

 the series of growth changes, figure 8, representing the cochlea 

 in such a rat, is inserted here. 



In the next stage, twelve days old (fig. 9), the development of 

 the tympanic wall is much advanced. The cells lining the sulcus 

 spiralis internus and the-inner supporting cells have nearly their 

 mature form and arrangement in the basal and middle turns; 

 only in the apical turn many and slender cells remain close to 

 the inner hair cell. 



The outer pillar cell shows a remarkable increase in length so 

 that it is twice as long as in the former stage, while the growth 

 of the inner pillar is much less marked. 



Therefore the outer pillar is much longer than the inner 

 through all the turns. From this change in the pillar cells it 

 results that the nearly equilateral triangle formed by them 

 becomes unequal and its summit is shifted inward. In all the 

 turns we can see the tunnel of Corti and also the space of Nuel. 

 The hair cells develop further and their previous inclinations are 

 increased. 



Deiters' cells show a very rapid development, especially in 

 the cell body, which increases many times, the nucleus moving 

 upwards. The inclination of these cells follows that of the 

 outer hair cells. 



