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ANATOMICAL AND PHYSIOLOGICAL STUDIES 



ON THE GROWTH OF THE INNER EAR OF 



THE ALBINO RAT 



INTRODUCTION 



Since Alphonse Corti, in 1851, published his famous work on 

 the cochlea of mammals, studies on this organ have been made 

 by many authors and have produced fairly concordant results. 

 Concerning the postnatal growth of the internal ear, however, 

 systematic studies are lacking. Especially is there no investi- 

 gation, so far as I know, on the growth of the nerve cells in the 

 ganglion spiral, not even in the great work of Retzius. ('84). 



It was the special object of these studies, therefore, to follow 

 the growth of the cells forming the spiral ganglion from birth 

 to maturity and to correlate the changes in them with the ap- 

 pearance of the functional responses and with the structural 

 changes in the membranous cochlea. In the course of this in- 

 vestigation studies were made also on the cells of the ganglion 

 vestibulare, in order to see whether these cells differed in their 

 growth from the cells in the spiral ganglion. Both of these 

 ganglia are situated in the course of nervus acusticus, but have, 

 as is well known, entirely different functions. 



Thus determinations have been made on the diameters of the 

 cells of the ganglion spirale and of their nuclei at different ages; 

 of the nucleus-plasma ratios and of their growth in relation to 

 those of other portions of the membranous cochlea. For the 

 cells of the vestibular ganglion similar determinations were also 

 made. Finally, these results have been compared with those 

 obtained from the study of other craniospinal ganglia in the 

 albino rat. 



In presenting my results I shall begin with a description of 

 the changes in the larger portions of the membranous cochlea 

 and pass from these to the cell elements themselves, and then 

 to the observations on the ganglion cells and to the correlation 

 between hearing and the growth of the cochlea. 



