142 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON 



ages is 648 [x 3 and 723 [i 3 , or as 1 : 1.1, thus showing a rapid growth 

 of the ganglion cell bodies accompanied by but slight enlargement 

 of the hair cells. 



It is evident from these ratios that the ganglion cells are 

 increasing in volume more rapidly than the hair cells in area. 

 It is possible that the nervus cochlearis innervates the other 

 cells of the cochlea as well, but even if this is taken into con- 

 sideration the general relations remain the same. 



It follows from this that during the period between the earliest 

 appearance of the functional response (nine days) and the 

 attainment of the maximum size of the cells, the innervation 

 of the hair cells is steadily improving, if we may infer such an 

 improvement from the increase in the volume of the ganglion 

 cells. After the close of this early growing period the relations 

 are approximately fixed through the remainder of life. We do 

 not find, therefore, in the cochlea any relation which corres- 

 ponds to those found between the spinal ganglion cells or those 

 of the gasserian ganglion and the associated areas of the skin 

 during postnatal growth. This seems to indicate that in the 

 cochlea growth is fixed or limited, while in the body as a whole 

 it is more or less continuous, and the ganglion cells behave 

 differently in the two cases. 



In table 109 are shown the diameters of the inner and outer 

 hair cells and their weighted diameters. In the last column 

 is given the area of the cross-section of the hair cells. 



The ratios of these areas on the initial area are shown in table 

 110 in comparison with the volumes of the ganglion cells on the 

 initial volume, and indicate that from three days of age the 

 values for the ganglion cells are increasing more rapidly than 

 those for the area of the cross-section of the hair cells, and at 

 twenty days the increase in the case of both elements has reached 

 a maximum. Here, as in the case of the cylindrical surface, 

 both elements show like phases of growth, but the increase in 

 the volumes of the ganglion cells is much greater than the increase 

 in the cylindrical area or cross-section of the hair cells. 



As it may be desirable to use for comparison the measure- 

 ments on the cells of the ganglion spirale as here reported, the 



