84 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON 



In both the rabbit and the cat the height increases at ten to 

 eleven days very considerably, as it does in the rat. Only 

 there is a large difference in the absolute values for the 

 three animals, these being largest in the rabbit and smallest 

 in the cat. The final average values in the cat are nearly the 

 same as those in the rat at the same age. 



Kolmer ('07) finds in the calf the value in the highest point 

 of the organ of Corti in the region of the innermost Hensen's 

 cells as follows: 



In the basal turn, 84 [A 



In the second turn, 90 JJL 



In the third turn, 105 [JL 



Average, 93 [i. 



Hensen ('63) gives in man the average height of the papilla 

 as 90 (JL in the hamulus and 60 [j. in the radix. Thus the height 

 of Hensen's cells is different in different animals. 



When we consider the growth in the height of Hensen's cells 

 we can picture the change of the form in the papilla spiralis. 

 As shown already, the height of the pillar cells is largest at the 

 earlier stage, when the papilla has its highest point at the summit 

 of the arch of Corti, and slopes downward to the Hensen's cells. 

 But at twelve days the form is reversed, and the highest point 

 is in Hensen's prominence from which the surface slopes inward 

 more or less steeply to the surface of the pillar cells and the 

 inner supporting cells. Thus the surface of the papilla does 

 not run parallel to the basilar membrane, but makes with it a 

 sharp angle opening outward. This angle has been measured. 



14- The angle subtended by the extension of the surface of the 

 lamina relicularis with the extended plane of the membrana basilaris. 

 As just stated, the lamina reticularis after the earlier stages 

 is not parallel to the membrana basilaris, but forms an angle 

 with it. The measurements of this angle , were taken as 

 shown in lines 4~4' i n figure 1. In table 58 (chart 26) are given 

 the values for the angle in degrees. Before nine days there is 

 no appreciable angle. From twelve to twenty days the angle 

 increases rather rapidly, and after twenty days continuously 

 but slowly. The ratio at the bottom of the last column shows 

 this clearly. 



