24 IRVING HARDESTY 



this zone must determine almost wholly the possibilities of 

 vibration of the different regions of the membrane as well as 

 of the membrane as a whole. The axial zone being attached 

 upon the vestibular lip of the spiral limbus and varying very 

 little throughout the length of the membrane, can hardly have 

 much to do with the variations in ''natural vibration frequency" 

 of which the membrane may be capable. In trying to compute 

 the areas of the transverse sections of the outspanning zone, it 

 was thought fairer to use for one dimension its width as found 

 in the teased out and unshrunken membranes. Other dimen- 

 sions had to be taken from the sections regardless of whatever 

 shrinkage the zone had suffered in them. Using the widths 

 obtained from the teased out membranes as the widths of paral- 

 lelograms, the depths used were averages obtained from six 

 measurements of the thickness of the zone taken upon the trans- 

 verse sections of the different regions of the coil at about equal 

 intervals between the outer edge of the zone and the edge of 

 Huschke's teeth [HT, figs. 1 to 4). The first measurement 

 was taken in each case near the outer edge and the last at the 

 edge of Huschke's teeth. Of the several cochleae used for the 

 purpose, these sections were used which were judged as pass- 

 ing nearest the apical end of the membrane. The areas of sec- 

 tion of the outspanning zone in each region were thus obtained 

 by multiplying its width in the teased out membrane by the 

 average of its thickness in the sections. 



Proportional volumes of the two ends and variations in the 

 volume of the zone were most desired, and for such, realizing 

 that by any further procedure the results could be only approxi- 

 mate at best, it was considered most feasible merely to multiply 

 the area obtained for the section of the zone in each region by 

 a given short length, say one millimeter of the length of the 

 membrane. The volumes thus obtained vary as the areas of 

 the sections. The areas obtained are as follows: 



Transverse section of apical end 61,723.20 square micra 

 Transverse section of 3rd half turn 43,293.45 square micra 

 Transverse section of 5th half turn 18,442.14 square micra 

 Transverse section of basal end 1,719.35 square micra 



