12 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON 



Distance 6 is that between the outer corner of the inner pillar 

 and the inner corner of the outer pillar. Distance 8 is that 

 between the habenula perforata and the outer corner of the inner 

 pillar cell. Distance 9 shows the radial basal breadth of the 

 outer pillar cell plus the outer pillar. Distance 11 shows the 

 radial breadth of the membrane basilaris comprising distance 

 5 (zona arcuata) and 10, which is the radial breadth of the zona 

 pectinata of the membrana basilaris. 



ON THE GROWTH OF THE COCHLEA 



As noted above, I have selected from at least seven serially 

 sectioned cochleas in each age group, four for this study, taking 

 one section in good condition from each labyrinth. From these 

 four sections the average values were taken for each age. Table 1 

 gives the data for the rats used here. As we see, sometimes two, 

 sometimes three animals were used at each age to get the four 

 best-prepared sections which corresponded. Determinations 

 accordingly to sex and side, therefore, cannot be based on like 

 numbers. 



In the following text we shall often refer to the I, II, III and 

 IV turns of the cochlea. This calls for a word of explanation. 

 As the cochlea of the rat has nearly 2^ complete turns, four 

 cochlear canals are usually obtained in the radial vertical sections, 

 as prepared by me (fig. 3). Therefore, turn I does not mean the 

 first complete turn, but about the middle part of the basal 

 turn; turn II about the beginning of the middle turn; turn III 

 about the middle part of the middle turn, and turn IV about the 

 beginning of the apical turn of the cochlea. Usually the cochlea 

 has been divided for description by the authors into the first, 

 second, and third turns, or more definitely into the basal, middle, 

 and apical turns. For the purpose of this study, however, it 

 is desirable to adopt the divisions given above, because here 

 measurements are largely employed, and there are some differ- 

 ences in size, volume, and arrangement of structures, even between 

 the beginning and end of the same turn. 



At all events, it is to be kept in mind that such divisions are 

 arbitrary, as the changes in the elements take place in a graded 

 manner. 



