GROWTH OF THE INNER EAR OF ALBINO RAT 169 



2. The computed diameter at birth is 20.3 [x for the cell body 

 and 11.7 ^ for the nucleus, and at 546 days, 25.3 and 12.2 n, 

 respectively. Therefore the cells at birth are comparatively large 

 and increase in size very slowly, but the increase is continuous. 



3. The increase in the ratio of the cell body is as 1 : 1.3, of the 

 nucleus as 1 : 1.1. We have between the same age limits no such 

 small rate of increase in any other cerebrospinal ganglion studied 

 in the albino rat. This small ratio indicates that the cells in 

 the vestibular ganglion are well developed at birth. 



4. We find no appreciable difference in the diameters of the 

 cell bodies or the nuclei according either to sex or side. 



5. Morphologically, the cells at birth are well differentiated. 

 The form of the cells is ovoid. 



6. The nucleus-plasma ratios are large at birth and increase 

 regularly with age. 



7. Comparing the development of the function of equilibrium 

 with the growth of the cells, we see that these are correlated. 



Final summary 



This study is concerned with the age changes in the organ 

 of Corti and the associated structures. The changes in the 

 largest nerve cells which constitute the spiral ganglion and the 

 vestibular ganglion, respectively, have also been followed from 

 birth to maturity. On pages 116 to 124 are given the summary 

 and discussion of the observations on the growth of the tympanic 

 wall of the ductus cochlearis. 



The conclusions reached from the study of the largest nerve cells 

 in the ganglion spirale appear on pages 143 to 145. On pages 

 155 and 156 are presented the results of the study on the correlation 

 between the response to sound and to the conditions of the cochlea. 



Finally, the observations on the growth of the largest cells in 

 the ganglion vestibu'are are summarized on pages 168 and 169. 



It is not necessary to again state in detail the conclusions 

 reached in the various parts of this study. 



At the same time, if we endeavor to obtain a very general 

 picture of the events and changes thus described, this may be 

 sketched as follows: 



