GROWTH OF THE INNER EAR OF ALBINO RAT 



137 



Schwalbe ('87) and Alagna ('09) find these ganglion cells 25 

 to 30 [a in diameter in the guniea-pig and cat. 



Alexander ('99) has also reported measurements on a series 

 of mammals, but as the size of such cells is greatly influenced 

 by the method of preparation, and as our averages are based 

 on the largest cells while those of other authors have been ob- 

 tained in a different manner, it seems best not to report the other 

 values in the literature, as they are sure to be misleading. 



TABLE 106 



Showing the changes with age in the diameters of the cells and the nuclei of the 

 spiral ganglion ahid the lamina pyrmidalis of the cerebral 



cortex, respectively 



days 

 1 

 20 

 546 

 Ratio be- 

 tween 1 and 

 20 days 



Ratio be- 

 tween 1 and 

 546 days 



CELL BODY IN 

 THE LAMINA 



PYRAMID COM- 

 PUTED DIAM. 



11.4 



18.7 

 17.0 



1 : 1.6 



1 : 1 . 5 



NUCLEUS IN 

 GANGL. SPIR. 

 COMP. DIAM. 



7.9 



10.2 



9.4 



1 : 1.3 



1 : 1.2 



NUCLEUS IN 



THE LAMINA 



PYRAM. COMP. 



DIAM. 



9.4 

 15.7 

 13.8 



1 : 1 . 3 



1 : 1.2 



days 

 1 

 20 

 730 

 ratio 

 of lto 

 20 

 days 

 ratio 

 of lto 

 730 

 days 



Considering the course of growth in these cells, we find it to 

 be similar in both the spiral ganglion and the lamina pyramidalis 

 of the cerebral cortex (rat) as reported by Sugita ('18). In the 

 former the cells attain at twenty days of age, the time of wean- 

 ing, their maximum size, and then diminish slowly with advancing 

 age. The cells of the lamina pyramidalis also reach their full 

 size at twenty days, and then diminish in the same way. There- 

 fore, the course of the growth of both of these groups of nerve 

 cells coincides. However, I do not know of other instances 

 of the phenomenon. When tabulated, the relations here noted 

 appear as in table 106. 



The difference between them is only in the absolute values 

 of the diameters of the cell bodies and especially of the nuclei, 



